Peter Navarro has been a critic of US trade policies, with a particularly strong focus on China and Germany which have large trade surpluses with the US. He teamed up with Wilbur Ross, who Trump selected for the top job in the Commerce Department, to order tariffs on imported steel and aluminum. Ross had been a very successful investor. He had invested in Trump's Jersey City casinos that were failing. He convinced bankers and other investors to go along with Trump's plan to deal with the failing casino's. The team of Navarro and Ross convinced Trump to announce his tariff plan against strong opposition from Gary Cohn who announced his resignation as Trump's Chief Economic Advisor.
There has been a lot of criticism in the press about Navarro who is not a top tier economist. The Wikipedia article I linked above on Navarro provides an excellent overview of Navarro as well as comments by economists and others about the use of tariffs and their relationship to national security issues which Trump used to justify his tariffs.