@JordiGH I think there are multiple factors at play, but the two main ones are direct correlation to how music makes you feel and reproduction of codified music tropes.
How the music makes you feel: for example fast tunes makes you feel energetic or in a hurry or tense, because there are a lot of information to process. On the other side I can't imagine a sad tune having really fast paced beats. So that's one thing.
@JordiGH These codifications, these tropes, reproduces themselves and mutate slowly.
At least, that's the way I see it.
@JordiGH the second thing, reproduction of codified music tropes:
When you watch a movie, some choices have been made to associate a particular situation/scene with a music.
The goal is to convey a particular emotion. So initialy people simply used what made sense.
But with the massification of such medium, codes emerged. Now, when you hear a specific type of music, you associate it not only with the scene you're watching but also scenes of previous similar movies you watched before.