Rizk was always a good site to me when I still played, never had problems withdrawing even big sums of money.
Insane win by the way, did you manage to withdraw it?
It just boils down to being lucky essentially. Some factors like choosing high RTP and your preferred volatility games may have a hand in your session going well or not.
This game really seems to dish out some serious wins! Big congratulations, hopefully you will use the money on something else rather than giving it back to the casino.