His fiance also stated that he wasn't a big drinker. Let's wait for the post mortem.
He may not have been habitually but he’d been drinking since 12,30 ish and by accounts his friends were pretty much intoxicated by the time he left, I expect he was too and possibly felt the effects much more. Him not being a usual big drinker may also explain why he may have become intoxicated quicker and more prone to accidents and poor judgement. Actually Lucy’s statement says a lot.