I'm pretty sure they were making a nice income of 100,000$ / month. if not more.
why they close ?
They ain't making that kind of money. Be realistic about it, not all 300,000 visitors would be losing all of their money. They are closing for a reason that no one wants to buy their casino. Maybe because they are tired of it, or maybe bankruptcy.
having 300,000 visitors doesn't mean they have 300,000 participants
and if the number of winner exceed the number of loosers then they will have a red signal, especially if some dudes made a high profit
and do not forget a hack or one of the team members running with a part of the fund?