I would be speculating here, but perhaps his talk of tariffs is in lieu of advocating a colonial empire (which he sort of is doing anyway, with talk of taking Greenland). Colonial empires don't need trade as much, because they've seized the resources they need.

Economic self-sufficiency can be prioritized in lots of different economic systems. Many of the more outlandish utopian societies aspired to be completely self-sufficient. Modern-day culturally homogenous self-isolating groups will strive to be near-completely self-reliant for non-economic reasons as well (perhaps epitomized by the Amish). The article I linked to above noted a number of very different societies that aspired to autarky, or as close as they could come.

My point wasn't to agree with Trump, but rather to point out that this does seem to be a genuinely and consistently held belief of his. He seems to sincerely believe that international trade involves countries taking advantage of each other - or at least letting themselves get taken advantage of by allowing individuals and companies make those international deals. I think he actually believes that America will be the stronger country if it trades a lot less, and even then on only egregiously favorable terms.

We'll soon see. A lot of folks appear to have thought that Trump was indeed using tariffs as a means to accomplish goals unrelated to trade, but it appears that he genuinely wants to seriously alter U.S. trade flows.