Why would a guy with a girlfriend ask to take me out?

I really like this guy but I found out he has a girlfriend which I did not know until I got told the other day. I would have never known luckily we have mutual friends though. He’s very attractive and I don’t know what to do, he told me he only stays with her because she blackmails him and threatens him if he leaves.

he messaged me yesterday asking to take me out next Friday and to go to a hotel with him and I really wanna go but am I bad for this? He’s told me he feels trapped because she harms herself if he try’s to leave. I mean I’d hope he’d leave his girlfriend if we did get serious but she does manipulate him.
Why would a guy with a girlfriend ask to take me out?
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