> why else would a ~billionaire that could easily fund it himself pull in that many investors that early?

Investors can be good for funding but they can also be good for education. Later, they're also very good for strategy.

> What happened to the good old way of figuring out product market fit first? Is that the only way a product can succeed nowadays

Generally it's very challenging. I have two products I'm building this way and you face a lot of up-hill climb where people with VC backing are getting the door opened for them. Of course, because of those same pressures to deliver and succeed, it's equally possible those same doors will eventually get closed on them.

I think Mitchell also lives in a bit of a bubble now. He went from friendly open source guy to very rich friendly open source guy. That's no knock on him, but I would consider viewing business from the perspective of someone who has been a CEO, CTO, and IC at the same company (his company) as his only job who became insanely wealthy as a result. I have a friend who has largely only worked in big tech, and successful startups, who tells me all the time level and salary don't matter to him. They don't matter to him because he found success early. Again, not a knock but sustained success will shape how you view the world and how you play the game.