Saban coached the 2003 LSU team. That's about the time that the SEC's top tier separated itself from the pact of P5 conferences.
It does feel like college football has changed since the SEC's ascendence these last 20 years. I'd say the SEC has only had 2 dynasties during that timespan -- Alabama under Saban and UGA under Smart -- but the championships from the other 3 teams in such a short timespan is notable. Saban and Smart have been able to raise an entire team to championship caliber. I'd say the other championships were the result of a truly remarkable talent surrounded by a good supporting cast (Tebow, Cam Newton, Burrow).
To me, an interesting question is how did each of these exceptional talents migrate to the same conference? After all, Burrow grew up in Ohio and had ties to Iowa State (his dad coached there). Surely you've noticed that ESPN promotes the SEC relentlessly -- how much of a recruiting factor is ESPN's partisanship? Is the ascendence of the SEC top tier related to the emergence of brain injury concerns (some states are shifting emphasis to other sports). Is this ascendence correlated in some weird way to some change in the NFL? Is it related to the SEC's organizational structure or conference leadership? I just don't understand how to contextualize all the data -- but it is a phenomena. The Sooners picked up on the trend and decided it's time to join the SEC.
Oklahoma is interested in championships. We think we can compete in the SEC at that level.
You need to dial back to 1998. The start of "sorting the championship out on the field." The first year of the BCS. That was the sea change that revealed the SEC as the premier conference in college football. Might have been the best conference prior to that, but we mostly weren't "sorting it out on the field," so every sports writer and coach got to vote as they (objectively or subjectively) wished.
So in the BCS/CFP era, 1998-present, the SEC has won 15 national championships. The next nearest conference is the ACC, with 5. The B10 has 3, and the B12 has 2. The PAC got none.
Not only that, but six different teams from the SEC won those 15 championships. That is unprecedented.
You want to try to define it as Nick Saban and the 13 dwarves, because that's what made you feel warm and fuzzy when you were in another conference. But Nick Saban isn't the sea change. It had already happened by half a decade when he arrived on the national championship scene in 2003.
As for the question you spent most of this post pondering, why do the lion's share of the most talented players choose SEC teams? Well, that one is simple. No mystery. They want to (1) compete for championships in college, and (2) have the best shot at an NFL career. And the SEC provides both.
Will Oklahoma compete for championships now that you're in the SEC? Maybe. I would be shocked if you didn't try. And by try, I mean spend TONS of $$$ to get the right coaches and support staff to have a shot. I don't think you have that now, but I fully expect you to try. It may take you a few rough years to figure out you're behind the power curve.
As for whether you succeed, well...there's a LOT of competition at the top (and at the middle) of the SEC. You're not used to that. That's another culture shock you can only adapt to with time. I don't know if you'll ever pull it off. But I wish you luck trying, except when you face us.
Go Vols!