Not an economist, but I am a mathematician.
It is 100% BS. 99.999% of the rich don’t get/stay rich by spending money. They buy a mega yacht and create a few hundered jobs for a couple months at best.
Economies grow when money moves. A billionaire spends 500M on a single yacht and that 500M moves to the yacht manufacturer and their suppliers. That same 500M spent $50 at a time by 10M people spreads that money across hundreds of thousands of businesses at minimum. That means it can be spent by more businesses on paying labor or expanding stock. That is more people getting money to spend money.
The concept of “trickle down” economics should function just as well as “trickle up” economics, but that requires that the wealthy spend as liberally and as widely as it being more spread out on the bottom. This the failure point. It will all end up at the top anyway, it will just make the world a better place getting there if it starts at the bottom.
Yeah, I hadn’t gotten into the “how to fix” part. Estate taxes, VATs on intermediary products, and wealth taxes are all great ways of redistribution, which is required for a functioning economy that grows at all levels, not just one.