I've heard the theory that this is bargaining chip. the idea being that the US will agree to drop the tariffs if other countries agree to buy more treasuries. And that this is a long term plan to lower interest rates, and help our fiscal crisis ...not quite sure how that all lines up, but I hope there is a plan!

But there is always the possibility that the 'people in power' are just being vengeful assholes. That has happened a lot in human history.