a hallmark of fascism and dictatorships is the capture of media, and the censorship of it.
i find it hard to accept that the solution to your problem here is that democracy must fall because of propaganda, when the very same propaganda is what leads to dictatorship.
Without a way to create objective dialogue, what is any system of government other than the picture it paints. Facts, and nothing else, is the only way to maintain a democracy.
Once you permit subjectivity, conjecture, and propaganda, like, say... when right wing billionaires buy create fox news, buy cnn, john oliver, colbert, every local news network (sinclar), washington post, tik tok, twitter, etc etc etc etc etc........ democracy is no longer possible.
In the US, social media has been captured by propaganda not because an authoritarian government has made it so through law and violence, but because the consumers like the propaganda.
The current situation is the result of free speech and consumers being able to choose the kind of content that they enjoy.
It is hard for me to avoid the conclusion that your argument in effect logically implies that free speech should be further curtailed and that elites (but the Right Elites) should be in control of the sources of content.
Which is a defensible position to take, actually. But people generally don't take it because reduction in free speech and consumer choice is anti-democratic. So the essence of this position is actually that we have too much democracy, not too little.
what is your solution tho? only government-sanctioned speech allowed, for the sake of democracy?
You just need to go one step further. The fear of billionaires buying media is used to justify increased government control of media and ultimately leads to a ministry of truth.
Once the ministry of truth gains power, democracy is finished.
The extremely unpopular citizen's united supreme court case was in many ways a last ditch attempt to prevent the creation of the ministry of truth. It likely won't last.