Only if they voted for Trump. Many didn’t. This election saw a lot more young people, especially men, move to the Republicans. In fact if you want to blame a specific demographic then blame men.

Because we can’t build a lot of car parts in the US for the same price. If we tariff imports / move all manufacturing back to the US then prices must rise. The problem is that this sucks up money that would otherwise be spent on other things, so the economy on the whole suffers. One way that advanced countries adapt to this is by pivoting to high-tech manufacturing… which requires highly skilled labor and can’t be easily replicated in other countries. In other words let someone else make a cheap widget, then use that to build a jet engine that increases the added value of the widget dramatically.