It's tough being a Challenger-level player. I got to chat with a few folks over at the Singapore CH. Basically, most of these guys can't travel with a permanent coach... they simply don't earn enough to do so. So when you've got a bunch of players grinding it out on the Challenger Tour, they kinda stay on the same level if they don't get enough coaching, particularly during a tournament. Which I'm sure doesn't help when we're talking about AAAA-level players.
I 100% agree about this, if you get stuck at the challenger level for long enough, you're overall level gets dragged down to that of challengers because that's what you're used to playing against, you don't have the experience of playing better players with better balls, and that experience is needed to give an insight of what a players needs to improve to reach that level. And when you don't have the coaching there with you to keep your game improving from week to week, you stagnate. But again, the true top flight talents don't get stuck at the challenger level because they're just that much above it, it's basically a test, and some guys pass it and others fail.