That’s actually not as obvious as it might sound. The thing is, as far as we know, light seems to have no mass¹. No mass means no inertia. So, if it accelerates at all, it should immediately be at infinite speed. But for some reason, it actually doesn’t go faster than what we typically call the speed of light. And we assume, that’s the case, because that’s actually the speed of causality.

So, it’s reversed. It’s not that light is just the fastest thing and as a consequence of that, nothing can be transmitted faster. No, it’s actually that there appears to be a genuine universal speed limit and light would be going faster, if it could.

¹) Light is still affected by gravity, e.g. can’t escape from black holes. We do assume that gravity is just a ‘bend in spacetime’ because of that, meaning even any massless thing are affected by it, but yeah, we’re still struggling to understand what mass actually is then.