The 40 year old ID-ing the women he has sex with at a party is icky for sleeping with someone half his age (double so if he is specifically looking for 18 year olds), but that is not illegal. Should that be lumped under rape culture though? Should sex work in general be lumped under rape culture?
If she was not 18, regardless of if she had a fake ID, it is still statutory. There is no mens rea required for statutory. It is however harder in such a case to secure prosecution and conviction.
He may very well have known his friend brought an underage girl to sleep with him, or asked him to find probable underage girls advertising as 18 for plausible deniability. He also may have paid his friend to pay for prostitutes for the party. I won't give Gaetz the benefit of the doubt on anything, but the article doesn't indicate any of those things happened.
At least we got a conviction for the person with the least plausible deniability, because we rarely get that unfortunately.