Another vector is takeover requests via their name squatting policy (that's how I got my username). But those requests shouldn't be approved unless the old account really is inactive. Might have been approved by mistake.
Yeah, but it's not like he did something nefarious. He found an account that was inactive and requested it from support and they gave it to him. If the previous user complained, either he would get to keep it or the previous user would get it - it wouldn't be deleted/disabled and they probably would have communicated something.
No, from my experience even a single empty repo disqualifies you from takeover. The point is to prevent name squatting, i.e. registering a name and then going nothing with it.