TRT is a factor, but the number one thing that Hendo had in spades is his H-bomb.
That power never left. Everyone he faced in the later years knew the fight could end with one shot and couldn't get comfortable dragging the fight out. His accuracy and timing also seemed to stay longer than most. Give Hendo enough time and he would land a big shot...several against Bisping.
BJ's striking became less of a threat in the last several years. He never really had devastating power, but he did have speed and accuracy to rely on. Look at how Yair got so comfortable being able to do whatever he wanted to do in that fight. BJ offered zero standing offense and couldn't even threaten a take down in order to do some work on the ground.
I think that the disappearance of respectable speed, and power is also what finally brought Randy's career to a close. His ability to grind out the dirty boxing became much less of a threat and he didn't have enough power, speed, and timing any longer to keep guys at a respectable distance.
Getting old sucks. You don't realize it, but you do lose a lot of speed and reflexes first. The power might remain as well as the strength, but you won't be anywhere near as quick as you once were. It is tough to admit. At 42 years old, I still mentally think I am younger, but my body reminds me quite often that I am no longer in my twenties. I think this is also what keeps tricking these aging fighters into staying active. Their minds and bodies are not in sync with where they really are physically.
