Someone working on a doctoral thesis can parse out the details, but part of explanation for continued success of successful coaches is recruiting. Once a coach gets their program to A+ (or sometimes even A), they begin to get their recruits for free. And they are top recruits at that. It's a rare circumstance when a coach fights a superior program for a recruit.
A couple of examples: I just moved to UMass in the A10 in IBA, arguably the best conference in that world, to play with the big boys. When I recruited a kid and saw that La Salle was after him, I gave up and pottle got him uncontested.
In Rupp, I worked UConn up to A+ and had my way with recruits from New England. (rshy, a very good coach, BC because, among other things, he was tired of having no chance for top recruits and having to settle for whoever UConn didn't take.) For UConn, that produced a stretch of a Final Four, a couple of Elite Eights and a couple of Sweet Sixteens.
One (and a half) bad recruiting seasons changed my fortunes, but I'm building it back and hope to not make the same mistakes again.
But recruiting is a significant factor in continued success. Not surprisingly, in HD, the rich get richer. If you have a team full of top players and get some top recruits, you have a team full of top players.
Any analysis of top performances starts there.