I don't have a problem with billionaires per se, but I do have a problem with them being able to spend unlimited amounts of money to influence politics and undermine our very system of government.
Congratulations. You have discovered the fundamental problem with democracy - it is simply just not that hard to throw around a little power, money and influence and lull people into voting for you.
It is actually quite difficult, which is one of the best things about democracy, but if you spend enough money over enough decades and infiltrate or destroy enough institutions, social norms etc. anything is possible.
Also, at least in the US, it's the side that spent a lot less money that won. Just like in 2016.
Besides, having money is only one form of influence. One might also have influence from a massive federal bureaucracy, legacy media, Hollywood, academia, workers' unions, and other places.
While money is just one form of influence, it’s the most flexible. Those other forms of influence can be bought, just as everything can be bought.
We may instate rules to prevent such buying. No problem, undo the rules because undoing rules can be bought because everything can be bought.
Look at something like Citizens United. Does anyone want that outcome? Not really. A few, very rich, people want that outcome. And so it is made. How we got there is unclear. What is clear, in my mind, is that the benefactors made it happen.
It didn't used to be until Citizens United. Before that point donation to a Political Action Committee was indistinguishable from donation to a campaign, and that decision created a distinction that the rich then ruthlessly exploited to fund campaign ads and paid speakers and paid writers on social media.
I do have a problem with most billionaires as their wealth largely comes from exploiting others (e.g. underpaying their workers, exploiting market anomalies etc).