And also put into consideration that more people are joining the blackjack casino, so there is every chance that reward would decrease over times since the number of users being rewarded from that pool have increased drastically.
Actually the total player has no effect on the prize because it has been set only the top 4 will get a prize so I think this is not the right reason
True, since the reward is rank-based, the number of participants won't have an effect to the amount of prize, unless the management itself decided to cut of the prizes just like what happen on the other casinos where their reward was cut to half.
Another thing to note is why new players come to Blackjack.fun obviously they have a reason well if what they expect is not available then they can just leave.
It is obvious, if new players are increasing, the marketing plan and advertisement of the casino is effective. And they have these features that these new players is looking for. I have read the recent post about rewards. Blakcjack.fun is to generous by giving bonuses if players are active in chat, participate in voting, and more. It is like a domino effect bonus where it starts on a fund deposit bonus.