They are lazy with the justifications because the justifications are irrelevant falsities.
The justification in this case ties into a known narrative that will work.
The tariffs have nothing to do with drugs.

If the reason for doing anything can be tied back to Ukraine, gun control, abortion, fentanyl, illegal immigration, LGBTQ, etc etc they will just lie and tie it back to one of the main issues that people are already talking about to get automatic support for the thing.

In this case Trump is heavily manipulating the economy and all the reasons for why he wants to do it are mostly unknown. Best guess is that he's creating a crisis on purpose to create a dump/pump scenario and start a fresh round of money printing.

Honestly considering how wishy washy he's being it almost feels like a day-trading paradise.