If you think about it, doesn't a successful coaching tree actually take away from the patriarch?
Like if anybody can do it, doesn't that mean your system is responsible for your own success? I could see if said coach was the architect of the system he coached, which Phil Jackson was not. But not just with Phil and Red. I'm looking at it like if the next man can step right in and replace you, then doesn't that mean you're replaceable?
You're supposed to coach players, not coaches. As long as my teams were successful, I couldn't care less about those trying to emulate me. In fact, low key I would probably hope they fail just to show my own greatness.