He likely doesn’t understand how they work (or if he does, is using it as a way to implement sales tax illegally).

That said, traditionally they are used to discourage US consumers from buying competition to US businesses, like the tariffs they’ve had on light pickup trucks for a very long time that contributed to the shitty choices decades later. Also these are typically targeted on select products, since as you’ve seen, blanket tariffs on all goods from a country fuck up supply chains and screw everyone pretty badly.

Both are bad, of course, just the latest ones are also very very stupid.