Corrections: Certain millionaires who see how bad wealth inequality is say they should be taxed more. Is this because they know if there is a collapse, they lose money and thus lose protection against very angry people? Probably to some extent, but still.
Capitalism is not perfect, but it doesn't always collapse. The flaw with capitalism is human greed. Making it a different system won't fix the underlying problem that some people want more than their fair share.