That's because natural test levels drop in old age, so TRT restores them to the former, youthful levels, between 200 and 1000 ng/dl. For noticeable benefits, enhanced athletes are generally blasting at 3000-4000 ng/dl, and that's just as a base for a complex and crazy strong cocktail of androgenic anabolic compounds.
My point is that PEDs really do take you to a different world physically, and there is zero - zilch competition between natural and enhanced athletes. When you are at that level, it's difficult to come off, go back to fatigue and weakness and small size, so you end up blasting for a decade and at that point your heart is the size of your head.