It's pretty logical that it's more the transfer portal than NIL, and it's got a lot to do with Saban leaving and even doing poorly prior to that. If you really want to see when the change happened, it was when Smart left Bama and UGA became a balance against Bama (except when we played Bama, LOL).
The SEC teams are paying the players just as much as the B1G. I'd say even more across the conference. What the SEC teams can't do now is stockpile talent the way they used to. But even that I am not totally sold on ... look at this year's recruiting. Look at who does the best in the portal. I'd have to see this over a 5 year period for this to really be something.
What I think is happening is parity, and that's a good thing. I've argued that here for years - seriously, I found posts going back to 2020 where I talk about parity that is coming due to NIL, transfer portal, and CFP expansion. This is what you are seeing. No one expected the SEC to dominate as long as they did. Geographically, they still will have the talent advantage. It will be interesting to see what happens when and if OU, UF, and Auburn become more competitive teams.
In the meantime, as a fan of CFB, I like parity. I like having teams like SMU, ASU, etc., making waves.