As I understand it, a "skilled" video poker player may do better than a novice, but still it's a machine, and it's programmed to make sure the house wins most of the time. Paddock evidently kept elaborate calculations telling him when specific machines had last paid out bigtime. But at least in 2015, he made a lot of money on that. How? Granted, he spent a lot of his time in casinos. But still, is that unusual?
One of the wealthiest people I personally know goes to Vegas every year, sometimes several times a year, because he's incredibly frugal and he gets a free vacation. He just has to give the casino enough action and he gets comped for the entire trip.
This can be done if you play perfect strategy in blackjack, bet on don't pass in craps, bet on bank in mini-baccarat, and if you play perfect strategy in video poker. The house edge is almost nil in these situations, so as long as you have the bankroll to handle swings, you are getting free food, drinks, rooms, shows, even free flights.
Most people don't play perfect strategy in video poker because it's counter intuitive. Say you get king of hearts, queen of hearts, jack of hearts, ten of spades and ten of diamonds. 99% of people drop the hearts and keep the pair as it's a guaranteed payout. Wrong, you want to go for the royal straight flush in hearts.