They’re also not very good at spending money on consumer goods when they don’t have any, which Amazon absolutely needs. (Tesla needs a lot of people above average income, given their cheapest offering).
And these two giants aren’t the only places people can work. (Not enough by itself, but still a massive improvement compared to the situation leading to the French Revolution).
Super-rich as a class exists because we let them exist, but there is a reason we let them exist… and a reason we have things like the SEC and FTC to stomp on them if/when they get out of line.