We've already replaced 99% of the workforce once. Now instead of subsistence farming, people can live, eat basically any kind of food they want, own a multi-room house, and fly around the world once or twice a year on a vacation, all in exchange for less labor than that same person would have needed to expend to simply not starve a few thousand years ago.

Is that because billionaires "give [you] money out of the goodness of their hearts"? Are you unemployed because all those farming jobs have been eliminated? Obviously not. Rather, the efficiency gains of modern infrastructure have simply made your labor that much more valuable.

It’s not possible to have “trillionaires” if the economy is so small it has unemployed people in it.

That’s literally the plot of Atlas Shrugged, not real life.

That's more a discussion of wealth distribution, systems of government and the flaws of capitalism. Theoretically speaking if you free human labor through the use of machines you're creating wealth because the same or greater output can be achieved with less resources and those resources can be allocated elsewhere. Of course some people believe that machines will replace all jobs eventually but historically that has not been the case. Generally new technology makes some jobs obsolete but humans adapt and find different ways to contribute to society.