There's always been plenty of former athletes, with football and "amateur wrestling" being a particularly common source of talent. Steve Austin's football heritage being an obvious example.
Difference is, most of those guys found their own way to wrestling. Rock and Roman come from pro wrestling families, Nash gave it a shot after his ball career was finished. Kurt's an exception - he actually was recruited. He was also a freak who took to it amazingly well.
Basically these days, WWE views ex-athletes, fitness trainers, etc. with no prior pro wrestling interest as its primary talent pool. Whereas in the past the talent pool came out of other wrestling territories or pro wrestling schools. They want to have absolute control of their product, down to assembling their wrestlers from the beginning and optimizing them specifically for their style.