Funding conservative causes as a wealthy private individual does not make you a threat to democracy., American liberal progressives seem to repeat that notion and get hysterical about this any time it happens, while forgetting the sheer number of extremely rich billionaire progressive supporters of numerous causes they do favor. Are these people then not also threats to democracy? Or does this definition only begin to apply once a billionaire supports a thing you don't approve of?
He's not just funding "conservative causes" he's funding people who are contesting the previous election. He's giving money to people that believe the current government is fraudulent, so yes, that is a threat to our current democratic system.
And yes, billionaires who donate to "the left" are a problem as well. Any time enormous amounts of wealth and power are concentrated in the hands of a few people, it can't help but go against democratic ideals. You used the term "progressive" but both of the main US political parties have been bought out by wealthy interests, and I'd hardly call either "progressive".
If you've ever looked at leftist progressive commentators, they just as often complain of big money in politics for the democrats, or even for leftist causes.