Well, how many place has managed to get 200+ million bets in less than a year, Windice will be one of the first ever (not counting stake because they had 6 years of primedice worth of marketing).
There could be 50 people online, 100 people online, 200+ people online and it wouldn't matter, what type of bankroll those players have is the real question, people do not come to casinos and spend days and days every single day, they come here gamble for few hours, lose their money and go, casinos needs to keep finding new players plus try to make old players come back, hence the importance is not the live number but total bankroll gambled at that moment.
Credibility is not only measured by bankroll, how about older casino with big bankroll cause a many years ago bitcoins was 100$? Any data how many's online at leats proving that site or casino not death.