You're severely underselling the extensive wealth billionaires have, the lavish luxuries and pet projects they have. They build schools specifically for training their children, they hunt endangered species, they create survival bunkers and consume huge amounts of luxury commodities. Houses sit vacant, food is thrown away, and billions of people go without. The capital and money they own is significant, as money is used as a gatekeeper for consumption of goods and services. Taxing cannot fix this, nor can it stop the tendency for the rate of profit to fall. I don't know if you realize just how big a problem for capitalism falling profit rates are.

Secondly, with respect to the Congo, you're confusing the symptom for the cause. Imperialist interference in the Congo is what sets up compradors in power. They don't need taxation, they need nationalization and protectionism, as well as to do more south-south trade such as with China. Kicking out the US and Europe would do wonders for their domestic development, but this is kept difficult by direct interference from imperialist countries. It's why the US Empire has hundreds of millitary bases around the world. The Congo needs socialism.

We overproduce goods and services, and let them rot on shelves and destroy them when they aren't sold. We do not underproduce, and anyone that is familiar with industrialization and manufacturing can tell that we can satisfy the needs of everyone on Earth already with a socialist economy.