That's not how it works, in any gambling profession.
If you have an edge (like if this guys is legit better at handicapping WMMA than the bookie he goes through) and you use proper bankroll management, you'll never go broke, and will probably be a winner long term.
Professional "gamblers" have been around for centuries, making money. And it's because they're not really gambling. They're exploiting an edge, and doing it many, many times over to reduce the variables.
This guy has been winning for years. Does that mean he wins every bet? Of course not. But he clearly knows what he's doing, and isn't in danger of going broke. A few anecdotes of newer poker players going broke doesn't change that.