As for the mather of the brain not being nessecery. first the treu headless zombies are part of the aftershock mod so i wouldn’t consider them cannon, as for the brainless zombie they are discribed as missing part of or there complere face so there is a good chance that the brainstem and cerebellum are intact the exact parts that govern motor function and automated movement. we know from corpse discriptions that anyone that losses more of there head is doesn’t revive so i would wagere that atleast these two areas are nessesery for revivecation if for no other reason that they regulate shit like breathing and heart beat which if these brain areas where missing would complicate revivecation by a lot. what does seem nessecery thow is a functioning nerve systeem since the blob doesn’t seem to be able to directly controle muscels or atleast not to the pressicion required to allow for fluid movement.
as for skeletons, they are not actual skeletons they are zombies whose skin has turned to bone so they do have muscels and organs to keep them moving, the only exemption to zombies not using muscels to move seem to be the skeletal dog and the hollow but they seem to be verymuch the exemtion than the rule with the blob instead prefering to use muscle as much as possible.
We can figure out a few things about the blob hivemind and how it works:
edit:i mean blob intelligence in general an possibly a little bit about how the hivemind and induvidual blobs are organized.
It does understand tooluse in some compasity but not as we would envensision it. It has learned how to infect terran life and how to revive and than manitulate the corpses that it has to better serve it needs. And seeing that the mutantions only work on what is already there naturally the blob seems to understand and use bodies as tools but not anything outside of this since it makes no use of armor or any tools as we humans would define it exept if it is already in the body (CBM’s) or grows into the body (kevilar zombies) so it mistaces it as part of the body and uses it. We can also assume that the hivemind is the one thinking of and designing the mutations since we see the same forms over and over again and the individual blob infections in the zombies determines what mutation path souts it best.
our reality is not that hospitable to the blob but it compensate for this by infecting terran life which seems to be far more hospitable to it. However not all terran life is equally useful or even hospitable to the blob plants seem to be for as far as we know either completely unaffected by the blob or outright immune to it and arthropods seem to be less hospitable than mamels given that the blob can’t revive them after death, nor does it infleuence thier behavor of them as much as you would expect.
the blob can’t control the induvidual forms it has but does understand the importants of some form of control, going as far as to focus spicific mutations on this (zombie master and necromancer) and sending some luitenants over from its own dimentions. The induvidual blobs also seem to have some level of induvidual control given the whole friendly blob out of canister case and the fact that the mutantions aren’t chosen by the blob hivemind but seem to be determined by a blob infestation itself that looks at the characteristics of it’s host and than determines the best mutation path (taking physical condition of the host and any injuries into consideration.
based on the blob doing the whole open rifts in reality thing, the focus and use of the mutations the zombies take on and it sending over some luitenant we can safely assume that it’s goal is not mearly to infect as much terran life as possible but that for now zombification is the goal. as for why the blob inside us all doesn’t just kill us (which it could easely do) i think that it isn’t becease the brain and cental nerves systeem is still active but more likely the immunesysteem has something to do with. since the blob stays dormant and doesn’t do much in a living creature even staying below a certain percentage. I think this is in order to avoid a immunesysteem response since the immunereaction to such a widespread infestation would most likely end up killing the host but could damage the blob infestation to such a large extent that it is unable to revive the body. this would also explain the differences between how blob psychosis affected people during the cataclysm since people have different immunesysteems there would be a differens between people how much the blob could infleuence different people without prevocing a immune response. it would also explain things like the slow healer or imperceptive healer perk with the former having less blob inside them since there immunesysteem is more sensitive to the blob and the latter being possible outright immune to the blob or having neglegable amount of blob inside them thus they have non of the enhanced healing that blob infection brings.
the induvidual blob organisms intelligence or something more accin to prosessing power is determined by it’s size, this can be seen in things like the brain blob being far bigger than it’s other counterparts but also by the fact that small animals can’t reaminmate (there isn’t enough blob inside them to compute all the steps nessesery to revive the organism and run it effectivly) and by the fact that if you split up blobs enough they turn into blob globs which still move but are to stupid to achieve locomotion.
we know that there needs to be around halve a pound of blob atleast in a creature to be able to succesfully reivive the corpse otherwise the blob inside the body will simply die, the blob glob which is lorewise the smallest portion where we see the blob is alive but inmobile and unable to do anything. a blob glob weighs 0.529 pounds so it is possible that this is the smallest portion that pure blob can be at and still survive in our dimention without being killed outright by the condition here with the exeption being that it can survive in smaller portians if it is inside a organism or in it’s form that is in the water table but this is more acin to a spore than an actual organism
think of the zombies as just walking meat, not actual animate entities. the “body” is already long dead, the thing “moving” in it is the slime which is slowly eating away at the corpse. what looks like “attacking each-other” is actually just the slimes feeding on the corpse.They aren’t “hostile” to each-other per say, they’re just hungry.
This is why zombies turn into slime when in goo traps. They just have a higher concentration of goop in their body.
we know from the existence of zombie masters and the blob luitenants that zombies are animate entities eventhow they fall under the control of a larger hivemind. the best allegory we would have would be celles in a body, the zombies and luitenants and so on are there own entities that make there own disicions and take there own action on a micro/local level but they do so in a limitet capacity and while being heavely infleuenced by and part of the hivemind.
The way the hive network works with the blob may be different than that of others.
Like the triffids that act as individual hivemids with each Triffid heart. The Fungal Hivemind that acts as a singular.
The blob may be a collective hivemind. When a threat is active it comes together consciously to eliminate it, and once eliminated takes on a dormant instinctive role. Unconsciously following prime directives of consuming and expanding without realizing that it is consuming other hosts.
Remember the cells allegory. Every single organism has a capacity for individual action on a basic instinctive level. So just like our body with its many different cells might attack each other (and does as part of normal operations) different blob organisms might attack each other by accident (your zombie and blob example) or consume each other (blob can consume any zombie to make more blob). And there even seem to be types of blob that are disconnected form the hivemind: mainly the contaminants in the water and the goo traps in labs that seem to be programmed to just consume anything that steps in them blob or not.
Going by the official lore, and the fact that damaged Z variants (brainless, scorched, crawling) have at least a reasonable amount of tissue (particularly muscle) remaining - I’d say only serious structural damage prevents revivification. “Skeletons” are covered in a bony carapace, they’re not actually walking bones. Blob can repair soft tissue very easily, miraculously so. However, it doesn’t seem to be capable of reconstructing a body from scratch. So stripping flesh from bone (butchering) makes revivification impossible for obvious reasons.
With pulping, I’m guessing that you’re destroying enough joints and bones to make the body structurally unsound. Putting a skeleton back together seems to be well beyond the blob’s capabilities. I’m not sure it’s even capable of regrowing individual limbs. Flesh can be mended, modified, and mutated, but spontaneously generating body parts is beyond the blob, as far as I can tell.