The fact that we could lose arguably the best cornerback in the nation (Ben Morrison), and have a three star true freshman step in (Leonard Moore), while experiencing no dropoff at all, shows that he knows his stuff.
We were also playing two true sophomores at safety and field cornerback (Adon Shuler, Christian Gray), along with a lot of young talent at linebacker (Bowen, KVA, Ausberry, in addition to Jaylen Sneed finally stepping up his game).
There was also something about Bryce Young stepping in as a true freshman, and playing like a polished veteran, despite not having even a year of strength and conditioning under Loren Landow.
Also, even the "Kelly kids" who were seniors last year, were developed under Marcus Freeman as DC, and later, as HC.
Brian Kelly had virtually nothing to do with the amazing stable of running backs we have, and the WR production last year was done with transfer portal guys, along with Jaden Greathouse finally finding his groove as a true sophomore. The only WR he could potentially get credit for would be Jayden Thomas, but even then, it was Marcus Freeman and co. who developed him into a guy who became a pretty good WR3.
The offensive line was developed by Harry Hiestand and Joe Rudolph. Brian Kelly's buddy, Jeff Quinn, wasn't very good at all when it came to being the OL coach. If anything, Joe Rudolph's tutelage finally brought Rocco Spindler to become a solid player, along with Pat Coogan and Aamil Wagner showing what they were capable of doing.
In the end, player development looks much better under Marcus Freeman than it did under Brian Kelly. Coach Freeman will let the best players available play, and isn't going to have his "right kind of guys" automatically be granted the starting spots.