There is simple logic in it. Punish everyone, and then let them come to you asking for exemptions. Then he can demand things in exchange. After that it's "Pray I don't alter the deal any further."
UK already asked for an exemption and he said they should buy chlorinated chicken first. If every country responds in the same way and gives in he's making bank. If they respond with a boycott on anything American, especially digital services, things get bad.
Rumour goes the idea is to force others to peg their currency to the dollar in fixed exchange rates so they can stay the reserve currency and still re-industrialize. Tariffs are used to force others into that arrangement. With how trustworthy USA has been the last few months, countries are not going to be enthousiast about this.