It would be a big blow if they left, but it isn't like this is unprecedented. Every class has a few that wind up leaving. They end up regretting a close decision, feeling homesick, have family health issues, can't make the grades, or just don't like where they see themselves on the depth chart.
We are in an unusual position, though, where we took almost 2 full classes last year. We are not only bound to have, statistically speaking, more players leave, but we the large class itself could exacerbate the problem of players transferring in the first place. It's one thing if you're a backup with no hopes of supplanting a player 1-3 years ahead of you. It's quite another when you see that you're hopelessly behind another freshman. Add in another large incoming class, full of quality players across the line, and it becomes even more tempting to preemptively head out.
I'm not saying it is the right decision, or that he wouldn't have played, but you can almost imagine what's going on in their heads, and it is clear that it isn't anything about the program itself.