You mentioned guys coming home early due to that, but they're not even necessarily part of the program yet. They can't yet be guys who haven't lived up to expectations and aren't performing. You're talking about guys already in the program.
They've slowly been cleaning that up since day 1 in 2016. It was awkward because there were a ton of missionaries they didn't recruit. Now before you get mad and whine, THEN things didn't get better because of two different recruiting guys who had opposite problems. The first acted like a coach and wanted to be an actual recruiter instead of organizing. The 2nd let the actual coaches do whatever they wanted and talked him into offering anyone they wanted without considering the numbers.
Let's be real, there's kind of been a mess with both basketball and football since the mission age change too.
Then you get a few crappy classes and too many missionaries, like 2013 and 15. And coaches can't fix that quickly without destroying the dumb APR.
Then like someone said, there's the redshirt change which has allowed guys to stay longer. That can easily put you over by 5 scholarships in a heartbeat.
There's no one thing. There are a dozen things influencing it all. Some agre controllable. Some aren't.
Regardless, BYU would be wise to finally freakin let the program hire more support staff. Unfortunately we just had this huge virus thing and millions laid off. They're probably not about too start with MORE hires soon.