Prolly a combination of everything you've mentioned. If he's 5'11, NT and with a normal face, I could definitely see that happening if he lucked out and managed to be present at much more parties and among much more drunk women with lowered inhibitions than normal. Then, all he needs to do is focus on flirting with the uglier/lower general SMV chicks (that's why I purposefully didn't choose any of those specific answers, I would imagine it's him flirting with all of those types and more), low-key not taking no for an answer and being persistent as hell. There's 52 weeks in a year, so if he started partying every other weekend since turning 18, he'd be on 182 parties, meaning that he'd have to hook up with a woman on every other party or so, meaning about one hook up per month.