You can, but you need to be smart not to put all your money on a single game and on a single time.
That is the key if you lose, and you want to recover it.
Also, i saw a lot of people that at the time that they lose, they start to deposit more funds, and they start losing it all .
Yes, its necessary to adopt a good strategy when betting on sports games. In this case there was an upset on the games he bet, and that is part of the margin of error a gambler has to plan before betting, sometimes the unlucky teams unexpectedly win the game and you have to be prepared for this situation, holding an extra bankroll to keep playing and recovering the lost money.
In sports betting, house edge doesn't screw up our game, as we depend the games results, that are decided technically and not only by luck, so I think it's very possible to win in gambling by betting on sports, since a smart strategy is used, like you said, not putting all your money in a single or few games.
Sometimes the house wins, but sometimes, it doesn't.
But yes, most of the times, it is taking people's money when they do not even realize that they lost, maybe sometimes it happens because most of the gamblers just play because of the adrenaline.