Too many people are looking too deeply for a meaningful explanation. I doubt there is one. Trump is using foreign affairs to play domestic politics. The tariffs sound well to some of his supporters, and the narrow benefits accrue to some of his supporters*. I doubt he has bothered to quantify whether he has, purely among his potential supporters, made more people happy than angry.
There is one way in which I can conceive extending the explanation/excuse: Trump demonstrates that he is the person whose "offer" in negotiations amounts to not setting fire to the room everyone is standing in. Doing this on one chosen issue might be enough to scare various parties into offering more concessions on all sorts of current and forthcoming trade negotiations. Essentially, it is a ransom demand.
(*To recapitulate what I suppose nearly everyone who reads here knows/believes: with trade liberalization issues, net gains almost always heavily outweigh net losses and gains are widespread while losses are focused. The losers are affected very profoundly - a complete loss of employment and any prospect for employment in a one-industry region is not meaningfully offset by a few dollars' reduction in the monthly cost of a generic basket-of-goods. Trump at the least pretends to have those people's interests at heart; Trump's opponents basically insult them and tell them their way of life is dead and they should move on.)
