Great post SilverHaven. There is no doubt there has been a consolidation of talent in college football. If one did the analysis all the way through the top 100 recruits the results would be similar (i.e. the top 5 and even top 10 programs taking a larger % of the top x recruits than in the past). We don't just see the impact in seeing the same teams in the college playoff, we see it in the regular season when the average margin of victory for top 10 teams is increasing. There is a growing gap between Ohio State, Oklahoma, Clemson, and the average teams in their leagues.
I don't think we can pin the reason on any one thing. Playoffs, national recruiting, selling a path to the NFL are part of it.
I think Nick Saban is partially why this happened. Alabama got the top class every year for several straight years. Great recruits like Von Bell realized if they aren't going to Alabama they better go to another top program if they want a chance to win a championship.
I believe we would see a similar effect in college basketball if players had to stay 3 years. If all those one and done recruits at KY and Duke had to stay 3 years those programs and a handful of others would utterly dominate the rest of college basketball even with a 68 team tournament. Imagine Duke with Zion this year and next...