That seems to be a scam casino, I mean I've tried a lot of gambling websites and casinos and I've never encountered something like it, I think this is a scam casino, its obviously a big red flag you should be able to withdraw your deposit and your winnings anytime you wanted, in my experience you just need to deposit probably 10-20$ then you could start playing already then it would just depend on your earnings.
I mean yes you didn't read the policy, regulations, etc. but this wasn't a fair thing, in my opinion, 5x was just ridiculous, something is going on might be some kind of pyramid scheme they just didn't want you to get your money out and surely your going to lose all of your money in playing.
I guess just pick a trusted gambling website next time I mean we have plenty of trusted gambling websites here in the forum, plus you could easily report if you encounter problem since they are active here in the forum on the gambling seciton.
It is not scam as long as the terms is mentioned clearly in the ToS page of the casino, yes 5x of the deposit amount without bonus is insane but once you created an account in the casino means that you are agreeing with all terms.
All casinos reserve the right to have their own terms, so we as players should read all the terms and perhaps making a screenshot or an archive of the ToS before making our first deposit.
Although the casino also reserve the right to change their terms anytime but if the change is just to refuse withdrawal or to harm players in general then we can say it is a scam attempt.