You might have the wrong impression of being the main man, it's not always the leader. In Raptor's case, that's not the case. The one who is making plays for them is Kyle Lowry and he is the leader, not Kawhi. Since Kawhi is the main scorer, therefore Lowry will put the center of offense to him. Kawhi is not a leader but he is just doing his job to the role assigned to him. Raptors trusted him.
A lot of people does not know the role of a player, yes Kyle Lowry is the leader as per his role, and normally a PG is the leader of the team as he is the one who makes the plays for the team, but what they are seeing is the Raptors have change when Leonard play with them and they got their first championship.
If I am just an average fan, I would also think that Leonard is the leader of the team as Raptors always messed up before Leonard arrive.