Ask HN: What are some red flags for a CEO in a startup?

That isn't a contradiction. You need domain knowledge to know which problems to prioritize, in order to converse with customers, and generally to not look like an idiot. Customers will not trust the company if its own CEO doesn't understand the space.

I would also add that it’s important for a boss to know how to do the job of his or her reports, mostly because in order to judge performance you need to know what goes into doing a good job. If you don’t want to get ripped off by your mechanic, you need to know a thing or two about cars, and the same is true for software.