In the overall scope of things, injuries and other great teams are included. It even includes great management teams, which come and go over the course of 120 years. Even Red Aurebach dies at some point. This is probability theory; it holds true. Four samplings is too small; that's just an example. And also all things have to remain relatively equal.
But if there remains 30 NBA teams and the salary cap rules stay in effect for the next 300 years (10 samplings), then the Knicks should win 10 championships, give or take a few.
Maybe we'll be lucky and they'll win all 10 in the next 20 years and then go 280 years without one.
(Celtics of the sixties don't count cause there were less teams then and all things weren't equal; Aurebach held the league on his string.)