At the time Trump defused a very dangerous situation. After his visit North Korea markedly reduced its threatening activities. Once Biden and Harris came into power, North Korea resumed its misbehavouir.
The thing about Trump is that when it comes to real issues people know he means what he says. That is why Kamala had to give up her demands to change the debate rules last minute, because ABC and Harrisworld understood, if they don't give up the main attraction will walk away.
Trump knows exactly what he's doing, he is respected by world leaders. No world leaders could ever respect a bumbling cackler like Kamala Harris.