Because if there's one thing billionaires should be scared of, it's billions of people suddenly becoming estranged from the economy. Having governments pump money into the consumer demand side becomes a no-brainer once you're faced with deflationary depression and mass unemployment. Your investors then get taxed to give UBI to workers to spend money to keep your sales up. It's probably the one form of wealth redistribution that on balance would actually benefit billionaires.
That assumes a degree of forethought and worry about consequences that the current set of billionaires seems to be studiously avoiding - along with half of everyone else, near as I can tell.
They dont give a shit about angry masses. Nor is the angry mass a risk to them. They have money for arms.