I'm pretty sure they were making a nice income of 100,000$ / month. if not more.
why they close ?
Not really for 100,000/month. Remember (sometime casino have a lost).
Why they close? Did you read an information from
Rollin.io (BTC casino) is now for sale! ?
Basically, they worried about the high rollers who can eat up their bankroll so they closed the site. I also don't think casino profits are always constant and they will be gaining every month because sometimes if any big whales win then their profits will be minus side. Also, it looks like they failed to sell the site as well because of the high price.