That reminded me of a speech he made back in 2011 on treating the Chinese McDonald's.
Well, in the above video Trump already talked about taxing imports at 25% from China back in 2011, before Xi even took power.
He mentioned that Chinese businessmen told him that the Americans are stupid for allowing China to 'rip-off' the US, and he certainly felt insulted. As a nationalist, Trump wanted to be tough so that America will be 'respected' as a country again instead of being mocked at.
My point is, 外交从国民做起. You don't laugh at your customer for being 'stupid' to allow you to 'rip' them off, much less be arrogant enough to tell them that. How many Chinese mocked at the Americans for being incompetent/stupid/no manufacturing capabilities etc because of the huge trade surplus, or even at other countries for that matter?