Well he doesn't actually DO it. He just announces he's going to do it and then backs off, or makes some phony announcement of a "deal", but nothing is signed. Lately he's said there's just "too many people trying to negotiate with him", they can't deal with them all, so he's just going to make an announcement of what the tariff rates will be after 90 days.
Many people suspect he's doing it to manipulate the markets, as well as enjoying the sheer power of controlling world markets. Instead of "The Boy who cried 'Wolf!'", Trump has become "The Dotard who cried 'Tariffs!'", and with the same result. He's backed off so many times that NOBODY on Wall Street believes him any more.
Mostly, people are seeing Trump's complete mental decline, in public, every single day. Spouting conspiracy theories about a fake genocide that isn't happening. Attacked your allies. Pardoning every con artist and former government official jailed for corruption or theft of public funds.
The sheer open criminality of this Administration is mind boggling.