The lesson of the Smoot Hawley Act and the Great Depression it helped cause should teach us about the dangers of government intervention in the market.
I agree that there should have been a lesson learned about tariffs (but Trump is too stupid to learn any lessons).
Stupid or a genius? He is stupid if the negotiations he has started don't improve our trade. A genius if they do.
I don't agree with your vague generalization, extracted from this one example, that all government intervention in "the markets" is bad.
I did not say that all government interventions are bad. But to try to list those that are good or those that are bad would take too much time. I have a radical suggestion, that will never be implemented, get rid of every government intervention. In a short period of time the good and bad ones will sort themselves out.
The state can never straighten the crooked timber of humanity. I'm a conservative because I question authority. Conservative Revolutionary