No reason, they just informed me that I can withdraw just my deposit
At least you've got your initial deposit and you should be thankful with that, do you ask what could be the reason why they didn't give you your winnings? because of the KYC? for me it seems that could be the valid reason and you are lucky that they allow you to withdraw your deposit wherein most of the casinos do freeze your account not unless you submit your KYC
Yeah being thankful for the refunds of deposit alone is not good enough this is because the players have put in a lot of time and effort to win those games, I don't like the idea of casinos asking for KYC verification at the point of withdrawal that attempt is not clear to me and at such could be a pointer to a scam ahead since your funds will be licked while you undergo that verification.
And in most cases, the verification will not go through and the player will have to wait for a complaint such as this one, which shows that the casino cannot pay a high amount even though the player won fairly.