Moderator: I would add #5 to the possible explanations. I call it the Trojan Horse Pinata theory:
5. Trump, or an advisor, realized that the Koreas, China (maybe even Japan and Australia) are moving to leave the US largely out of Asia's rapidly emerging economic integration; and they are baiting Trump's protectionism with honeypots -- a techie term of a trap -- to help speed the process along. The TPP pull out, unilateral "trade wars" -- stupid, and the emerging Asia alliances are taking advantage of it.
Keep Bangin on that Giant Pinata, T'ump! There's nothin' inside but old laundry.
Why a Trade War With China Isn't 'Easy to Win' (Slightly Wonkish)