I’m amused at how he did everything wrong according to conventional bootstrap wisdom - rushed straight into developing, didn’t do any interviews or create a landing page first, never did direct sales, but succeeded just fine. There’s something to be said for the power of an audience - if you’ve got 40k twitter followers who cares about marketing :p.
Looks like this is his third product, and having an audience of 40k potential users is a great head start. But yeah, not a lot of audience research or anything to see if people wanted it, just “I think I’d want it”, which sometimes works wonderfully and sometimes is a dud. Kudos to him.