Billionaires in the United States control $4-5 trillion in wealth. Their collective wealth is trillions less than a single year of government spending. The deficit in 2023 was $1.8 trillion. In 2019 it was $985 billion. Allowing the 2017 tax cuts to expire might raise $400 billion before the impact of slower growth is factored in. The tax increase to bring the deficit to ~2% of GDP would be astronomical. The Biden spending largess has to be rolled back. Federal to state abuse of Medicare funding has to be cut back. The United States was a wealthy, first world country in 2019, cutting spending is far easier done than trying to find $2 trillion in tax revenue sitting under a rock.
It isn't just the sheer wealth they own it's their influence on our politics and how they destroy any chance of actual democracy or a government that works for the interest of all, rather than the interest of the few.
But keep in mind it isn't just the billionaires. It is a relatively large group, either complicit in their hoarding of wealth or at the very least unbothered. Presidents like our good man Teddy understood this. They saw first hand the power of the wealthy and just how little influence a president can have if the monopoly capitalists had their way with America.
Obviously our politics are unrecognizable from that era. Every single president is now owned by corporations, banks, and/or the military industrial complex. They are bought and given opportunity to lead as long as they tow the line. You can look at one topic alone to see just how true this is: Every President's stance on Israel since the 70s. This isn't the only rule they are required to obey but it's the clearest and most obvious one. Even the "left" hopefuls like Bernie Sanders know they have to play this game and really softball the topic.
A lot of progressives and liberals think the Democrats can change the system from within and un-do the damage. I'm past that point, personally. Although I wouldn't hold it against anyone for not being so cynical.