He run his business all his life.
He has run businesses into the ground his entire life. Trump Entertainment Resorts, Trump Ice, Trump Institute, Trump magazines, Trump Mortgage, Trump Ocean Resort Baja Mexico, Trump Productions, Trump Shuttle, Trump Steaks, Trump Taj Mahal, Trump University, Trump Vodka, Trump World's Fair, Trump: The Game, Trumped! all went bankrupt. Even when he was running casinos, where the house always wins, he went bankrupt four times! He has nearly as many bankruptcies as felony convictions. Add to that he's an adjudicated rapist and a self-confessed paedophile.
There are a few reasons for it
The US has now proved that it will elect an utter moron and then allow him to do whatever he wants. Clearly the US is no longer a country to do any business with.
Trump just announced that he will induce 10% tariffs because he got mad at the courts..
And now it's 15%, despite the US having signed deals with many countries promising tariffs at 10%. Clearly the US can no longer be trusted to follow through on any deals signed by taco Chump's minions, so there's no point bothering to try to negotiate any deal. Or at least not until November, after that adults will be in charge in the US.