They just asked you to submit your KYC details? Simple as that?
What are the other things they told you about the specific violation that is written on their Terms and Conditions?
I'm totally good if KYC will be asked to me if it's about big winnings but the site should explain clearly to me the case I got involved in.
Sending your personal information to someone that you do not know on the Internet is never a small or a simple thing, also this casino as described by the OP does not really have a good reputation, something that even the quickest search in the forum could have told us so you could avoid playing there, in that case sending your personal information is even harder as who is going to trust that those people are not going to sell that information on the black markets?