I understand that gambling services do not organize contests here just to give money to forum members for free, so I often play with the money I have won. And yesterday I had a pretty successful evening: I spent the 20 usdc I received to buy free spins in the sweet bonanza game, then increasing the bet again and again...
Thus, 20 usdc turned into ~455 usdc. I just decided to stop there.

Going from $20 to $455 and deciding to stop there, you are very lucky with your bets, and maybe professional too, but by stopping there you are very disciplined and can be called as a Responsible gambler.
Not many gamblers can do this, they can win or even win big but at the end, by irresponsible gambling, they lose a lot of money and can not use won money for enjoy with something in life.
The screen shows like you got it after 15 bets, am I right?
Congrats with the win Xandry and impressive that you could stop after that win. As Octradism already mentioned, not a lot of people would be able to stop as they would keep on playing in the hopes of getting lucky again; I know I would keep playing a bit and still cashout some profit but it would not be as much as what you did.