We already invented that. It was called the 20th century. Tried wealth caps, nationalizations, revolutions - you name it. Usually ended with gulags, breadlines, or both.

Billionaires are a symptom, not the disease. You don’t cure a fever by smashing thermometers. If we want fewer billionaires, we need systems that don’t reward monopoly power ¯\_(ツ)_/¯