I'm not using MMA math in my logic. I'm saying the younger fighters like Hendricks, Lawler, and Woodley were catching up to him. After a reign like GSP had, people watch the tape, practice how to counter what GSP does best, so if you can neutralize his best offense, or defense you can beat him. Hendricks proved this.
GSP knew he lost that fight, that's why he made a rash decision, and didn't know when he'd come back. Bottom line, we wouldn't look at GSP as the GOAT had he kept fighting. Because he would have ended with 2-3 more losses.