I think there's been a lot of talk lately about cheating or fixing bets. This is always going to be a possibility whether we like it or not. Whether it's an online casino or a brick-and-mortar establishment, it doesn't matter; cheating can happen in both. But cheating isn't as easy as just saying it, since these sites are often audited or monitored.
So you can rest assured that almost always, whether you win or lose, it's largely due to your own luck.