Their heads are not empty. They are filled with believe in an individualist notion of the subject and accordingly in individual freedom beeing maximized in a free market. This ideological branch is called liberalism and it's been hegemonial for about 80 years, mostly under the brand neoliberalism.

Those 2 central believes proof more and more dysfunctional, but the threshold to overwrite them is high, regarding the consequences for ones social identity, how to view ones biography, friends, role models, etc.

The democratic party is neoliberal, the republican party as well, MAGA might have some neo-feudalism and fascism added to the mix.

There is very little political organization among the majority of people, like in neighborhoods or at work (unions weak), that could provide socialist critique or the experience of lived solidarity.

Anti-communism adds to the threshold of reforming ones ideolocical dead end situation.

Here you go, a little praxeological explanation of why people are so "dumb", which is much better than saying they are idiots, at least when it comes to actually trying to better the world, when it comes to hope ;)