Documentary on this just now.
To me it seems that 3 men assaulted Stuart Lubbook. Barrymore one of them. All of them high on drink and drugs. Things got out of hand.
Lubbook was young and fit so it would need 3 men.
Lubbook was straight and a stranger to everyone. The three gay men may have found out he was straight, maybe through Lubbook himself. If Lubbook mocked them they may have wanted ro teach him a lesson.