Probably driven in large part by the expansion of the voting pool. Great political thinkers have no more appeal to the masses at large than Beethoven, Dostoevsky, or Linux.
So we get entertainers and silver tongued devils for politicians whose primary skillset tends to overlap heavily with that of conmen.
Speaking of figures with no mainstream appeal, Plato wrote extensively, and utterly prophetically, about this phase of democracy in The Republic, and how it will inevitably lead to tyranny. It's playing out as if from a script.
Trump's twice election certainly makes a case for universal voting, but maybe different individual vote weights?
Basic stuff, like if you don't know what 5 - 1/4 equals or what cells are. If not, maybe you shouldn't have as loud a say in choosing political leadership?
Universal voting is the opposite of the direction to go. See: Australia. Of course going in the opposite direction is probably impossible, because it's not about knowledge but about susceptibility to typical forms of manipulation, emotional highest among them.
This is the reason that politics has largely shifted from a game of knowledge and vision, to one of mud slinging, ad hominem, and appeals to emotion, fearmongering, and so forth. It's not because the electorate doesn't know enough, but because they have poor emotional control, making them easy to manipulate. It's exactly how conmen, operate with Wiki offering the typical pattern as exploiting "the victim's credulity, naivety, compassion, vanity, confidence, irresponsibility, and greed." [1]
Watching historical debates and speeches just makes me sad about the disparity with modern oratory.