TL;DR he is trying to answer the question of whether it is better to have cheap stuff to buy or have higher salaries.
About 50 years ago, globalism started becoming a thing. The idea was, lower barriers to trade and make the world a better place. Countries with cheaper labor would make good cheaply, and export those goods to developed countries like the USA. The USA in turn would shift from making things to providing services, making the country richer overall.
Everyone benefits - the people in the USA benefit from cheaper goods because they are imported from cheaper countries while enjoying higher salaries because everyone now has a cushy service job. The third world countries get to develop because they are selling goods for American dollars.
At least, that is the dream we were sold. But that's not the reality. Yes we can buy cheap stuff from Temu, but real wages have stagnated for decades - around the time that globalism was introduced. Globalism, as it turns out, was less beneficial to American consumers than it was to the corporations who reaped massive profits due to these changes.
And so for the last 50 years, globalism, and the things that it depends upon, namely elimination of trade barriers, have become accepted as normal and desirable. Nobody questioned them - nobody dared to question them. "Everybody knows" that tariffs are bad and being protectionist is bad and globalism is good, and just don't question it okay?
Except, as it turns out, globalism has its problems too, and one of that, if you aren't protectionist, you allow your own industry to become decimated, and this leads to depressed wages for the people in your country. This is exactly what has happened and exactly why Canada charges such high tariffs on dairy imports from the USA - it is trying to protect its own dairy industry.
This is what Trump means when he says that those trade deals are unfair. They were created when the countries in question had smaller economies, and so it "made sense" to protect them from American imports. But now it doesn't anymore.
Trump's whole plan is to shift manufacturing back to the USA, so that the USA becomes a net exporter again. He knows that he only has a limited time in order to accomplish this, because anything he does could be undone by the next administration, especially because he is using EOs to accomplish them. That's why there is such a rush. It gives everyone 3 years to see if the new normal is better than how it was before. I wager that it will be, but we're in for 3 years of pain. Then expect to see wage growth takeoff like it hasn't in a long time.
If the mainstream media is telling you that tariffs are a Bad Thing, that should make you very skeptical.