My take on why dimensions go "KABOOM!" in smatsv (pretty lengthy)
It's obvious as fuck that the black hole has been caused by Spot. What really baffles me is HOW NO OTHER spider-person noticed. There were a lot of them when Miguel caused destraction of the world where he replaced his alternative self. Some of them HAD TO notice. Just look at how other Miguel's world collapses and how Pavitr's.
Miguel's seems to glitch out of existence.
Pavitr's is being engulfed by a black hole.
It's clear as day. They either:
1. Ignore the facts, purposely deceiving themself, because they don't want the idea of interdimensional villain to come true.
2. Genuinely trust what he says, because they truly believe, that even if he is not right he has every dimension's best interest in mind.
3. All of them are complete idiots with some serious eye problem, making it impossible to see the OBVIOUS differences, even if those were to slap them in the face.
Here's what I think caused this disaster. Miguel in some sense replaced canon with his own, while the old canon was still "running" in the background. Basically it looked like that - two Miguels in one dimension for long period of time. The original Miguel is dead. That's the original canon. The impostor took his place trying to cover that death. But that didn't erase it. So, there was Miguel who was dead and at the same time the one who's alive. We don't know at what point in time the other Miguel decited to play pretend, if it was before or after the death was known, but he did it. One timeline tried to marge with the other, but couldn't (one was rejecting the other), causing real life glitch.
With Miles the situation was different, because his canon was actually rewritten, not replaced. The spider didn't replaced the original because that one was dead for years, and it died itself too, preventing further changes. No major glitch happened because the dimension adjusted to this by killing Peter. It was small change. Not a string of constant changes like in Miguel's case. Miles's dimension still exist only thanks to him and the others stopping Kingpin's plan. If they failed, then this world would be destroyed too, because one canon would tried to actively rewrite the other without being able to, once again. The same situation happened with Pavitr's world.
The factor that contributed to the change cannot continue to interfere with it continuously:
Miguel - replaced his other self, kept doing it by living the life that didn't belong to him, the role that played major part in lives of people from that dimension.
Spider - bit Miles, died, couldn't bit anyone else (his venom was not working after it's death either), it played no other role in the story, showed up years after the previous one, caused a mojor plot point but not participated in it later.
Miles - took no previous part in the world's canon, changed important plot point, did not participate in further events.
In conclusion a small, one time changes are ok-ish, as long as they won't be a constant thing that keep happening.
