It's been a while since I've seen a player get that much preferential treatment.
GIannis forces players to foul. He's not part of the need to shoot a 3 at every opportunity (although he shoots more of them than he should, but really cut them down in the finals). He goes to the rim and pretty much does it every time he touches the ball. You can't play him one-on-one or he is almost always going to either score, get fouled or both.
At 7ft, he's doing things the guys guarding him can't do and can't handle. Ayton was lost trying to defend him and fouled accordingly. So, you switch a guy off that can stay with him quickness-wise and he takes them right to the block and abuses them because of his power/strength.
On top of that, he plays harder than anyone on the floor. You can't half-a$$ or even 90%-a$$ against him or you will be fouling him. For the most part he doesn't complain about every call like half the league so he doesn't take himself out of plays by throwing his concentration somewhere else.