I think beginner accounts that have a high win rate are intentionally given to them to attract beginner accounts to come back the next day. But that doesn't seem to be the case for most of them because only the truly lucky ones will win the big bucks. But we also don't know what casinos do to attract newbies and we only know casinos do promotions to get more newbies playing on their sites.
sometimes its called beginners luck ? but I also believe that Casinos online are giving those chance so new accounts will deposits and play more as they already experienced winning and trying to believe that the probability is higher on that site to win, also why online casinos are very strict in using multiple account because it is not usually because of the abuses from bonuses and events , instead it is because of that given wins for new accounts.
I maybe wrong but at least this is how i see things here.
I've been experiencing this kind of beginners luck too I created an account and then i manage to win a good and profitable reward in a lot of games but after a few weeks it does not get a good outcome but of course i limit myself with this I guess there's part of an algorithm for their first-time users to get the courage to play more but another factor to having a good odds of winning is the RTP which is the higher the ideal profit to the users at the same time that's why it is more good for the active gambler the odds is in favour to them.