It is a coincidence. The rotational speeds of planets formed through a lot of chaotic events in the early solar system. E.g. Venus spins in the "wrong" (retrograde) direction, completely violating conservation of angular momentum, probably because of a planetary scale collision.

We can try to explain solar system formation through mathematical models and simulation (Phobos and Deimos would be clues) but we can't go back in time and find the real explanation. No law of physics mandates that Mars' rotational period should be similar in magnitude to Earth's.

I don't know why you got downvoted but I couldn't find anything helpful regarding your question. I found some references to the fact that mars and earth have ~24hr days but no explanation as to why they are so similar. Mars also rotates (on its axis) the opposite direction of Earth which I found interesting. So many questions about our little local solar neighborhood, so few answers!

I'm pretty sure everything about the particular properties of our solar system is, strictly speaking, a coincidental result of the initial conditions of the big bang. But to speculatively address the intent of your question, I'd guess it has to do their relatively similar size, solidity and distance from the sun.

I'm not sure the premise is correct. Why can't it be coincidence?

I suppose it could, but of all possible values, it seems exceedingly strange that they'd fall on essentially the same number. It seems much more likely that it has basic physics behind it, but I'm not sure what it is.

random chance is as good as physics. the earth was hit by a mars-sized impactor allegedly, so if not for the moon, we would have a completely different day length. (assuming there would be some 'us'.)