I don't think it's about money, I think he just doesn't find it satisfying or he might have something more interesting in the horizon.
Based on his life thus far, he seems like the kind of guy who's always looking for that next challenge or goal. While he clearly enjoyed commentating as long as it lasted, it probably isn't his passion in life and it took up a lot of his time with travelling, background research, etc.
I mostly enjoyed his commentary barring some slightly annoying habits. He really did his research and I especially liked the way he informed viewers what the fighters should or want to do in each situation.
I think I'll come to miss him.