I have such mixed feelings on the transfer portal.
For the vast majority of players, just suck it up, earn your stripes, and let the process play out. I have no intel as to why Knuth, the SD QB Transferred, but I assume it is because he didn't want to ride the bench for 3 years behind Athan. Fast forward, he would be the leader in the clubhouse to be QB1 for the next 3 years.
The transfer portal is also a great thing. Lets assume Athan lived up to the hype. Knuth could decide do I want to be a career backup or transfer to a school that gives me a better shot to play. He only gets one chance at college football. I don't blame him for going to a school that gives him a better chance to play.
There are a few positions - QB is the main one - where the backup just doesn't play. We joke about Fleck keeping AK in the entire game, but that isn't abnormal for the vast majority of teams from JV High School through the NFL. It isn't a position like RB, WR, DL, etc where you can rotate guys in and out to keep them fresh.