Oklahoma has won the last 6 Big 12 championships. They have lost a total of 6 conference games since 2015.
In 2010 the final ESPN college football ranking had TCU at #2, Oklahoma at 6, and Oklahoma State at #13. Texas was not ranked in the top 25. IIRC TCU had several first place votes that year.
2011……..Oklahoma State at #3 or #4 depending on the poll, Baylor finished at #13, TCU finished at #14, Kansas State finished at #15, and Oklahoma finished at #16. Again Texas not ranked in the top 25.
2012……K State finished #12, Oklahoma finished #15, and Texas finished #19.
2013……..Oklahoma finished #6, Baylor finished 13, Oklahoma State finished 17.
2014………Baylor and TCU finished #5 and 6# respectively, and KState finished #11. Oklahoma AND Texas were no where in the final top 25.
2015………Oklahoma finished #5, TCU finished #7, Baylor finished #13, and Oklahoma State finished #20. Again Texas finished out of the top 25.
2016……..Oklahoma finished #5, Oklahoma State finished #11, and West Virginia finished #17.
2017……….Oklahoma finished #3, and Oklahoma State finished #14. Texas again out of the Top 25.
2018……….Oklahoma finished #4, Texas finished #9, and West Virginia #20.
2019…………Oklahoma finished #7, Baylor #13, and Texas #25.
Iowa State finished #10 IIRC this past season.
My point is, yes The Big 12 will take a hit when Oklahoma leaves, but they will survive. So if you look back at the last 10 years, Texas leaving for the SEC doesn’t hurt the Big 12 like losing Oklahoma in terms of league strength, but they do lose a team with a rabid fan base.
The Big 12 will still have several big time football programs that are tough ball clubs year in and year out. Iowa State, K State, Oklahoma State, TCU, West Virginia, and Baylor. Getting UConn gives the Big 12 a real shot in the arm in men’s and women’s basketball, and a football team with a fan base that travels to many away games. Say Fresno State!!!!!’