Seems tautological. I think what he's asking is, why is there to be a limit to how fast light can go, and he's looking for a better answer than "because there is one." I would love to know why there's an arbitrary speed limit to lights that (from our understanding) spacetime doesn't necessarily have to obey.
Well, yeah, it is tautological. If there weren't a limit on the rate of information transfer, everything possible would happen instantaneously and there would be no way to really experience anything. Call it selection bias if you like. The speed of light is like the rate of time; it is because it can't not be in any meaningful way.
This isn't to say that, given the tenets of simulationism, we can't hypothesize an "external time", and describe the rate of our universe as some amount of Tx/t. But the fact that that's an amount of time per time should also demonstrate why it's a meaningless concept in-universe.
Actually there's two questions here; the question I think he's asking and the question you think he's asking.
The question you think he's asking is: why is there a limit to how fast light can go? For this we have a reasonably good explanation; it's more or less a consequence of basic geometry once you've understood relativity.
The question I think he's asking is: given that we have a value of c why is it that value of c and not some other? For this we have no damn explanation, it's just an arbitrary constant that got baked into the universe for some reason. Perhaps one day we'll understand it in terms of something else, but perhaps it's just as in-principle unanswerable as "so why the fuck is there a universe in the first place?"
