Ask HN: How are startups finding their markets?

Maybe this is just my ignorance, but I cannot possibly see how any of the recently funded YC start-ups could ever turn a profit.

They all follow a common trope - offer an AI solution to a niche problem with a generic pitch (leveraging LLMs.. RAG pipelines.. so on so fourth)

Now this is fine and all since they managed to obtain funding, but after looking at their respective founder profiles, a little less than half seem to have actual domain experience regarding their start-up market. I am not saying this to discredit them, as they all have incredible achievements in technology and management, it is just interesting to see.

How are they able to find their markets and respective problems that need solving? Are these companies even viable, or are they just a pipe-shoot of quickly executed ideas trying to market themselves on the "AI hype"?