Mostly due to a few small things.
Lee bought a few material things, but he was mostly able to live out of his backpack for years at a time, at least before he got married. He didn't have many material desires (no fancy car, clothes, or big gaming computer). He periodically lived on other people's couches (including mine) between starting university and getting married.
I remember he drove through at least a few red lights because he was in the zone deep in thought processing some coding concepts / business plans in his mind while driving. Once I noticed this, I didn't let him drive me; instead he started to code on his laptop in my passenger seat.
When we were waiting in line to rent a UHaul-type truck, he was pacing the retail waiting area thinking through some coding for a future Unspam feature. I remember it because the guy standing behind me saw him as a stranger threat and started to get anxious that Lee was pacing in a hoodie nearby. I mention it because he never concentrated much on the small daily tasks like waiting in line and mostly overloaded those tasks to optimize his long term goals (eg. startup success).
He didn't write big architecture docs (possibly the part of his work that didn't scale much), but his mental capacity to juggle lots of small facts and tasks was pretty incredible. It worked great with a small team with very low turnover. I miss those days when I just checked in with him 2-3 times a day rather than having to spend a lot of mental effort to figure out how to serialize lots of trivial stories/subtasks into Jira.