You generally know that some programs have a ceiling: Vandy, UK, Miss State, South Carolina, etc.
Sure, teams like Auburn or Florida are generally good. The SEC has 6 programs that compete for National Titles: Alabama, Auburn, Florida, Georgia, LSU, and Tennessee. Oklahoma had 4 of those programs on the schedule. SEC also knew that Ole Miss was up and coming.
They loaded Oklahoma with Alabama, LSU, Auburn, Tennessee, Ole Miss, and Missouri. South Carolina generally has a ceiling but their are typically better than teams like UK or Vandy. They gave them to Oklahoma as well.
Meanwhile, Texas got Miss State, UK, and Vandy all three (the three WORSE programs all-time in the SEC) as well as an Arkansas team that we know has been struggling lately. Florida had been struggling for a few years as well and Texas got them. In fact, Texas got both Florida and Georgia AT HOME and got Oklahoma in Texas. So the perceived 3 hard games on their schedule where all in the state of Texas.
Texas had no meaningful road game like Tennessee had with Georgia and Oklahoma. Texas had all 3 of the bottom tier SEC programs. They had an Arkansas team that had struggled recently. They also had their 3 toughest games in Texas. The schedule was just NOT fair no matter how you put it. Give Texas LSU instead of Kentucky or Ole Miss instead of Miss State and it is probably a more decent schedule.
Texas currently has 0 wins against the top 25. That is unheard of from a 1-loss SEC program.