I don’t think it’s as much ignorance as it is tribalism. Humans are highly tribal, by our nature. People believe what they are told by trusted authorities, by the trusted leaders of their “tribe.” People will be skeptical of anything that doesn’t come from a member of their own tribe, even if what they’re being told is based in facts and evidence. Politicians have known this for a very long time, and they use it to their advantage. They just have to convince a group of people (usually one that feels alienated or disenfranchised) that they are “one of them,” and then you can steer them in the direction you want them to go, usually by pinning them against some other, opposing tribe.
Conservatives and liberals are opposing tribes. They don’t like each other and they don’t trust each other. All Donald Trump and other conservative politicians have to do is present positions that are in opposition to liberalism, the ideology of their hated enemy tribe, and members of the conservative tribe will quickly adopt them, not out of ignorance but out of tribalism.