Billionaires have power for two reasons:
* there is an enormous need for capital in modern economies
* everyone else refuses to actually keep any capital. Individuals max out their credit cards instead of saving. Voters demand tax cuts so governments are borrowers instead of lenders.
You can tax back the capital, but there are 2 issues doing so: as long as it's spent and not saved, it will rapidly end up back in billionaire's accounts AND in the mean time, the loss of investment when billionaires pull out capital to pay the tax will mean fewer jobs and higher prices.
These are the reasons no politician is willing to pull the trigger and go after the uber wealthy: you'll be celebrated for a week and then lynched when the economy falters.
You want to get out of this position? Require people to save and balance governmental budgets. But people don't want higher taxes, less services and lower spending power. At least they dislike it more than they like equality and opportunity.
If you really think billionaires have undue influence (and i do), cut your spending, invest and pay down debt and vote for higher taxes and lower state spending.