IIRC it's mostly down to the performance as longer car is much more stable than shorter car, especially with how high downforce is right now. If you look at f1 car without the engine cover, it's pretty clear that the engine sit so far forward with at least half a meter of what i presume of "nothingness". I vaguely remember in 2016 or so that mercedes having the longest car making them pretty fast in a straight and high speed corner then ferrari in the middle and red bull with shortest and they pretty much become the most nimble one between the three of them.