Why would any of this be a problem from the perspective of those who will own the remaining companies? They won't sell anything to normal humans who have no income anymore, true; but they don't need to, because their machines can produce for them whatever normal humans had been producing previously.

The preprint is interesting in that it predicts that on the way there, one can run into some kind of vicious cycle that leads to suboptimal outcomes even for the company owners. Navigating around this would certainly slow this process down, but I personally don't see it changing the ultimate outcome.