Agreed, CEOs are ideal PMs and also are actually responsible for leading the product too.
But I don't think business is something you can't learn. I'm a generalist specialised in design and marketing, yet I handle the product as well as help with financial planning because we're bootstrapped and early stage.
The more interdisciplinary work someone does, the more they learn and grow through experience from different domains.
Plus there are enough tools, automations and resources available for devs to leverage and not need large teams. Plenty of small sized teams in SaaS are killing it while still being lean af.