I blame coaches who got lazy in recruiting. In the 70s things would have been turned around had Jim Pittman not died. But in the 60s Texas was on TV more than any SWC team they would land all the top recruits - make each of them think they were going to start as a freshman - and that IMHO was why UT was successful and the other schools were not. Why we couldn't go 5-5 each year in that decade is, again, a result of lazy recruiting. Would love to hear Leap's opinion of this topic - a very good topic and an excellent question.
Frogs were best SWC team in the 50's with 4 titles and 5 bowl games (bowl games scarce then) and several All-Americans.
Then things began to change when Abe had health problems and wasn't recruiting like he had before.
Also, no limit on recruiting and Royal at Texas plus Broyles at Arky took 100 players each year to keep the other teams down.
Platoon football was coming and that didn't help the smaller schools to stay up with the big boys.
Frog football started to go downhill and we saw 25 or 30 years of being in the shadow of Horns and Hogs.
That is my take on the subject, and we are very fortunate to have survived to enjoy today's success.