Why do the dif regions have unique styles?

Why and how did NA, EU, APAC and CN develop different styles of playing the game?

It's just how it is. It really is a mystery.

But it's just different mindsets on different things. Every region has different working ethic etc.
That's my guess tho

Teams base their ideas, strats, and comps off what works in scrims. And obviously, NA teams can’t scrim EU teams. Therefore, NA teams develop their own identity when it comes to comps, plays, and general play style. Same thing for the other regions.

severe lack of international tournaments ESPECIALLY in the beginning of the game
therefore, regions started only playing against themselves, and there was no style to "adopt" in the beginning, so different teams made their own styles because there wasnt a dominant one yet
style is created, then that team starts winning in scrims = other teams in region develop to counter said style or adopt it
then that x4 for all the regions = four diff styles of play