i don't think 10 BTC is too big, especially for a reputable gambling platform all the way from 2014. Of course investing in such is risk but with risk comes reward if all things go well.
Who knows? Maybe the just wanted out.
Maybe the owners just wanted to move on to the next venture. The only people who know why the decided to shut down the business and sell it are the owners. Do you have any evidence to back you claim that it's a failed business?
If New owners came up with new good marketing strategies. Do you think they can't make any money out of BetBTC?