VCs fund companies. For them, employee compensation is a cost against their profits. In tech, this is the largest cost by far. The owners of capital deeply deeply deeply want a future where they can earn their billions without paying the rabble anything. AI is selling this idea to them.
Unfortunately, it isn't actually about being able to replace somebody from a technical perspective. CEOs are picked by capital and selected from amongst capital. An effective "CEO.ai" wouldn't be used for all the same reasons that an ineffective "Employee.ai" will be used.