The question is "what business value is AI driving?" and the answer was "a solo founder cut all the devs and still delivered a product".

Separate question: "now that AI is here and development isn't a moat any more, how does a business defend itself from competition?"

That second question is a direct result of AI. Five years ago the amount of cost and effort spent on software development was a moat. Now it's not. So that answers the first question completely, I think.

As for the second question - market sector knowledge, customer contacts and industry reputation, all the usual non-technical things that make a moat. Also, we may now be living in a world where software companies cannot expect to be monopolies in their markets any more. This company will have to compete with many similar competitors for market share, like in most other markets. I think this is a good thing. Less enshittification will ensue.