He won the Big 10 in 2016, but Ohio St., a team Penn St. beat and is in their own division that did not play in the Big 10 Championship game, was selected for the College Football playoff. That would not happen to USC or FSU.
Head to head, Franklin at Penn St. is 2-4 against Michigan, 2-4 against Michigan St., and 1-4 against Ohio St, all three in their division. He is 5-12 against the big 3 in his division and 27-4 against the rest of the Big 10 in the regular season.
Although recruiting has picked up at Penn St., he still lags Ohio St. and Michigan. Also, look at USC and Florida State recruiting compared to Penn St. The last 5 years on the field, Penn St. has been in an upswing, but FSU and USC have been in a downswing. PSU's average recruiting ranking over the past 5 years: 13.4. USC? 8.0. FSU? 8.4. So, even when USC and FSU are struggling on the field, they still out recruit Penn St when they are performing well on the field.
Look, Penn St. is a great football program, but they play in the Big 10 East, the second hardest division in college football after the SEC West. Put Penn St. in the ACC Coastal and they are playing for the ACC championship almost every year and a shot at the CFP.
Franklin may decide to stay at Penn St, but winning a national championship would be easier at USC or FSU.