I can only guess that once they get a ton of pussy they stop putting women on a pedestal, and hence stop giving a shit. Thus getting more pussy in return. Bodybuilding becomes more of a competition and or hobby at this point.
Mid life crisis perhaps, but no more then a successful athlete, Olympian or anybody that looks great and slowly starts to lose it. I don't see the crisis as such a negative thing, I am pretty sure I will have a mid life crisis. It will just be a restructuring of what is possible for me. I might be very sad because my greatest instrument is getting limited in learning speed, adventuring ferocity, sport dreams, weightlifting weight, etcetera.
And let's not forget that generally for older men it is a buyer's market
For women not so much, you enjoyed that in your 20's.