I Got Out of Tech and Still Make a Decent Living

I was really hoping for some explanation of how this person got out of tech and still makes money, but the only information they gave was "I have a little bit of savings, and some mysterious secret project I started is making 1/3 of my salary, so I quit my job". This was a thoroughly disappointing article. They don't say what their side project was, even vaguely, and they don't seem to be making all that much money either, contrary to the headline.