whats up with my fiancé and public sex

so i met this guy at a party last month, hes in his late 20s too. we got along great, and one night after some drinks he invited me to this underground club for adults only. it was wild, like full on kink stuff but consensual. so ofc i flirted around a bit, trying not to get carried away. then i saw my fiancé there, chatting with someone else from the party. i felt kinda weird but decided to talk anyway. next thing i know, he’s inviting me into one of the rooms for some private time. we ended up having rough public sex against a wall as others watched and cheered us on. it was intense and i loved every second. my fiancé is usually so reserved but this made him wild. i’m not sure if hes ever tried anything like this before, or what it means. anyone else have a partner who got into public stuff unexpectedly?