What we're really talking about here is administrative support.
Private schools sometimes view athletics as a helpful marketing tool, or are willing to invest some support for a quality coach. But if there's a waiting list, privates often decide to avoid being labeled "sports schools," preferring to be thought of as academic powerhouses -- and then the athletic support withers away.
For SJND, Shawn Hipol was doing what he was hired to do -- win games, just like Don Lippi did on the boys' side. But when SJND landed in the BCL-West, so it could affiliate itself with academic stalwart College Prep, and Head-Royce, Bentley and Athenian, a change of heart occurred. Now Hipol's winning ways were an embarrassment, and so they forced him out.
It was really unfair to Hipol and the basketball players, and certainly a smoother transition would have been easy to arrange. And now SJND is horrid in basketball, though whether that really matters to the administration is unclear.
As for Presentation, as long as Wade was there, there were enough good players to compete in the wider world, if not with Mitty, but the air went out of the balloon very quickly when he left. Pres does need to leave the WCAL, though I don't know it works in that section. (Can it happen in one year?)
Over time, I would expect to see somewhat less emphasis on sports at private and parochial schools, as there's no need to market if people are clamoring to get out of public schools and into privates. Some privates will stick with it, of course, as it's wired into their DNA, but others may take a step back.