Owners or investors of gambling site is different with online players. The former has already made a lot of money, while the latter is still playing and hoping to get rich. But both can justify that gambling is not wrong as long as you don't abuse yourself and just enjoy gambling and not make it a habit.
I don't think that owners already made a lot of money since they still gambles with the house bankroll. It is the same with investors. Ever wonder why some Casino goes bankrupt? Because their house bankroll were depleted. I guess both owner, investor, and player are gambling in hope to get profit if not get rich.
And I agree that gambling is not wrong as long as we have control in our selves and does not affect our lives negatively/