Probably by reading HN all day ;)

Depends on the intensity-level one puts in their 9 to 5.

I think that it allows him to invest into passive index funds (no active trading) which hopefully appreciate over time.

I think they are really saying that because of their dayjob, they can invest - and then that generates passive income

Maybe he outsourced his job to foreign workers and watches cat videos all day like this dude-

https://www.bbc.com/news/technology-21043693