Yet still most of the championships are won with man to man defense.
3-2 zone only works well if you have good shot blocking on your players. And good shot blocking means it is away from some other skill. Most of the time it is inside shot. So running good 3-2 zone already puts you to a huge disadvantage since you pretty much have 2 players on the court who can't score. Some teams manage to balance this very well but it's arguably much more difficult than having good man to man based defense.