I put the blame on the coaching staff. You can't explain that other elite players chose not to come to USC because there was no talent there, by blaming any player for leaving USC - because if there was no talent on the team, that means PJ was justified in leaving himself.
The first big thing why we weren't able to build off of the Final Four appearance, was losing 4-5 players the previous season due to off-court legal issues. That thinned out the roster of returning players, and when Carrera, Kacinas, and Chatkevicius graduated after that season, and then Thornwell, Notice, and McKie graduated after the Final Four season the next year, that left the roster with little experienced, proven players.
Then before the Final Four season, we lose Stroman, Gregory, Doby, and Cobb. After the Final Four we lose the above three seniors along with Tut, Keita, Felder, Gueye. That's just way too much turnover over the course of two seasons. We had to replenish the ranks via the original transfer format, which were JUCO transfers and graduate transfers, and the pickings back then were slimmer than what they may be today.
Frank Martin needs time to coach and develop his players into playing the type of team defense he wants his teams to play. So that heavy player turnover set the program back to before the two 25+ win seasons. And the staff wasn't able to capitalize on the FF by going after quality prep talent, to start the build-up over again. So not only do we not capitalize on the FF, but we have a number of mediocre seasons after the FF season - we've gone 75-72 (41-46) in the 5 seasons since 2016-17. If we hired a coach that goes 75-72 (41-46) over 5 seasons, it wouldn't surprise me very much if that coach got fired.......