Also consider the speed of light is also the speed of causality. If there was no such limit it means it would be possible for effects to precede causes which would lead to a very different kind of universe!
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No matter how fast an effect propogates, it is always after the cause (with an infinite speed, I guess effects happen instantaneously, but not before).
Of course, this doesn't fit with a universe described by general relativity, where time can be different for different observers. But you wouldn't have a universe described by general relativity without that constraint in the first place.
> No matter how fast an effect propogates, it is always after the cause (with an infinite speed, I guess effects happen instantaneously, but not before).
If everything happens instantaneously then there is no real cause and effect, and the universe would be over before it really got started.
Imagine a universe like Conway's way of life, where only neighboring cells can be affected in one timestep. Now add to it a rule that all blocks have a color, and the color of all blocks are changed when one block changes color. Now you have a universe with both immediate and non-immediate effects.
a hypothetical universe is mostly worth discussing seriously if there's a physics that is coherent, not just a mathematical landscape. At least it isn't that interesting in the discussion of universes, but might be in discussing mathematical ideas, but those do not necessarily mean there's a universe represented by it.