1) Trump has already been all over the place, endless cycle of trying to be tough and then caving. Also, admitted to relying "upon instinct" for his tariff policy. Pathetic. Zero credibility.
2) Trade partners don't believe he'll stick to his word and know hes a weak person, mentslly and physically. Stock investors know he's erratic and not thinking straight.
3) Trump views "deals" as a zero sum game. That's why he's ripped so many people off but also had so many failed businesses, despite being born with silver spoon and being (I admit) a gifted conman with excellent charisma. As a result, he's looking to "win" deals and even rip countries off instead of going for something neutral. As a result, he'll continue to fail in his trade "negotiations" just like his failed businesses.
4) Bond market sell-off yesterday showed our vulnerability. That's a big card that other countries have on us.