Herschel Walker fought a guy who has 2 career fights under his belt and had one after that. He fought a nobody who was never going to be anybody. The next guy he fought has now had a total of 5 career fights. He hasn't fought anyone since Walker. He's also a nobody. He was fed nobodies with little experience and little skills. He wasn't put in the cage with guys ranked in the Top 50 in the world in their weight class, much less Top 10.
And Brendan Schaub grew up doing martial arts throughout his childhood. He didn't just decide at 24 to get into the fight game. He had a pretty good background base to start with. He wrestled growing up. He was doing BJJ. He began boxing in high school.