I don't think it's that unrealistic. The trick will be, not going too fast, managing a few separate transitions, and making sure capital maintains control of the institutions with the monopoly on the use of force. The masses don't tend to act to project their interests until it's too late.

It does make sense, but you're not thinking about it clearly because you're too tied up in existing social structures. The end state "AI-fueled Elon Musks" (note that's a type, not a particular man) don't need common-man customers or their money, because they don't need to pay labor to operate their capital. They can directly operate their capital themselves, so they'll just do whatever the heck they want and nearly everyone who's now an employee becomes an ant.

At that point the main economy would mainly consist of billionaire ego projects and some trade between large corporations to support them. Common people would scrape by on billionaire largess and by squatting on resources not currently needed by billionaire ego projects and using it for small-scale subsistence production.