Consider if the US government liquidated every US billionaire at 100% of their stock market paper value (impossible, the liquidity influx would smash the stock price to the ground and ruin middle class retirements).
In this non-existent perfect world, it would raise about… $6-7 trillion. Enough to cover the US government deficit for under 3 years, or run the government for under one year. Then it’s gone.
Completely liquidating every billionaire would be satisfyingly cathartic, but still wouldn’t be enough to cause a real trajectory change. The idea is useful political fodder, to hide the fact even a hypothetically heavily taxed billionaire class can’t even cover today’s spending problem.