" younger Republicans I know are just about Trump though and, similar to Trump, don't really seem to hold any principles that underlie their views on any one topic"

This a big worry. I thought Trump was for old angry people shaking their fist at sky. The ones with dementia. Why are young into him?

I'm sure it varies in different parts of the country. I'm in the southeast, a very Republican region for the last 60ish years. I also have family in Arizona, not as red as here but still popular.

In both areas, the young people I know that are Republicans, and pay any attention to politics, seem to mostly be attracted to his energy and wild promises/claims. They also tend to laugh at the things that I expect many here are concerned by.

It's a bit less of a worry for me, because Trump is going to die before too many more years go by (like, just of old age; man's not young or healthy).

At that point, there's going to be a huge shakeup in the Republican Party, and the American right wing more generally, because from all indications, he's the only thing holding that coalition together, and they do not have a successor who could do anything like the same.