When was OU's last national title?
It's about resources. They have them.
OU has won numerous conference titles and played in the final four for the title more than once the last few years. Tennessee has done none of that over the same period.
Resources:
They have a big stadium, but they are not filling it any more, even before COVID. Here's an article about sagging home attendance over the past few years. They were down to averaging 77,000 per game in 2018 from over 100,000 a few years ago, following a multi-season path of shrinking ticket sales:
Tennessee football: Attendance down from last season's home opener (knoxnews.com)
A shrinking fan base = shrinking resources.
I don't know how SEC divides bowl/tv money with the team getting some of what they generate, but Tennessee has been generating a lot less of both.
Wins
I don't think you realize how bad UT has been and for how long. Over the past 10 seasons they have a losing record at 60-62 with virtually all their wins versus lighter weight non conference opponents (Georgia Southern, Austin Peavy, Western Kentucky, Akron, Troy) and the weaker teams in their conference division (Vanderbilt, Kentucky).
And with what's just happened I don't see it getting better. They have SEC conference $, but that alone doesn't make them elite. Tenneesse has a great history, and I supposedly have European royal blood in the family about 14 generations back, but I am not a blue blood and at some point UT is not either. I don't know exactly when that point is reached, but at some point a football program is no longer a blue blood. Interesting question.