Baylor's rise is not complicated. They are the only team that prioritizes pass defense in a cupcake conference. The remainder of the conference is not accustomed to that and basically thinks it is unfair. The Big 12 since 2007 has had the mentality that any swing pass or tunnel screen is entitled to 15 yards.
Baylor allows 5.8 yards per pass attempt. That is 5th nationally. For reference, the Big 12 leader in 2016 was 7.0 and then 7.2 in 2017. Baylor has gone from 8.3 in Rhule's first season of 2017 to 7.6 last year and now 5.8.
Is Clay Helton going to prioritize that type of evolution? Not a chance. He won't know or care. USC has been between 6.6 and 7.0 every season since he became head coach. It was 6.9 this year. Meanwhile it's already happening at places like Oregon, where Cristobal moved from 6.9 in 2018 to 6.1 this year.
The Pac 12 and Big 12 hired tinkerbell coaches for many years. You couldn't expect it to continue forever. Once these stingy coaches take control it's much simpler to made huge defensive and physicality advances than in prior decades, because so many coaches basically aren't even trying and adopt the fanbase mentality that all you need is a prancing offense via the spread.
Oklahoma has made advances in pass defense this season also, from 7.5 in 2017 to a laughable 8.4 last season to a decent 6.6 this year. Lincoln Riley knows he is supposed to do it, but it is kind of annoying to him. Notice the difference in TD/INT ratio between Baylor and everyone else in the conference: