Easy.
We had 5 national championships in basketball (more than UGA and UF combined in football, today) prior to the broad integration of college athletics in the 1970’s, and were established enough to go anywhere in the world for talent.
So winning is all it takes? UK wasn't recruiting at near the level Cal is before he arrived, Why weren't all those championships bringing the same caliber of athlete prior ro Cal if it was an easy answer? Cal gets kids to the NBA, it is pretty clear most of those 1 and done kids aren't all that interested in winning a championship. If one happens it's cool, but they have no interest in staying 2 years. So it is more about the ability of Cal to get them drafted than win UK another championship, Cal just happens to coach at UK.
I really don't think things that happened 50 years ago is revelant in any sport today, rules have changed too much.