Tariffs are happening because it's an idea he came up with 40 years ago when he was in his prime and it stuck to him.
And no one is doing anything to stop the tariffs, despite everyone knowing better, because the people in power can't tell him "no", because that would hurt his ego. You see what he does to people who hurt his ego? They get mocked on social media, deported to a foreign gulag, they and/or their spouse gets fired, their company gets investigated or loses grants, or their house gets raided by the FBI.
So everyone has to go along with it no matter how dumb it is.
Notice the date -- 2016. This has been brewing for a long time, and I will never forgive / forget that the people who recognized it and called it out early [1] were mocked and ridiculed to no end. They were shunned in their professions, called alarmists, and liars. But they were right the whole time, they were just ahead of the curve. If we had just listened to them, this could have all been avoided.
[1] https://medium.com/@Elamika/the-unbearable-lightness-of-bein... (also from 2016, as far as I know the first person to make the connection between Trump's narcissism and his inevitable attempt to become a dictator. She predicted January 6 five years before it happened just by pattern matching his personality disorder to dictators of the past).