This is going to happen almost every year as long as Cal and Krzyzewski are coaching.
Recruiting is more nationalized than ever. The best kids are funneled into the same events, with the same group of AAU teams, and/or go into the USA Basketball program when they're 16. Very few kids fall through the cracks, and even when they do, assuming they're discovered before they finish HS, they quickly end up in the same places as everyone else.
UK and Duke are the two most powerful programs nationally, with Kansas hanging in there, and Arizona still hugely prominent for players out west. What happens is that the very best guys' school decisions often come down to UK, Duke, sometimes Kansas, Arizona for some others/ or something else. UK and Duke are often basically almost half that equation, because the question for these guys is usually "do I want to play on the biggest stage, or do I want to try something a little different?" This means that UK and Duke have a HUGE margin for error. Either school can miss on 5 top 10 players, and still end up with a class loaded with future NBA players (see UK's 2015 class for a great example of that).
You're seeing this right now in football, too, where Alabama is practically guaranteed a top 5 class every season, and now Ohio State is headed in the same direction.
