Adam, I found this super compelling and am glad you shared it. Really sorry you're going through this.
One thing I just want to respond to is you keep saying you "feel like an idiot" for not being able to figure out a business model.
Two things:
1) Building a successful OSS-based business requires doing two near-impossible things: building a successful OSS project AND building a sustainable business. I've heard people call them "double miracle" companies. Building even TailwindCSS alone is an astounding contribution to software and the world, and you should feel proud of that. You are in the top 0.00x of people in tech just from that. I know that probably feels like cold comfort right now, but I still wanted to say it.
2) You DID build a successful business model. It worked. You hired a team and were profitable. You achieved the double miracle. Again, 0.00x of software founders ever do this. Then things changed in the marketplace. That is awful, and the timing sucks because it lasted much less time that you hoped. But it doesn't change the fact of the prior success.
Hope I'm not overstepping here, but I just wanted to say this. Been an admirer of yours for a really long time and it hurt to hear you going through this.