Because the taxes will encourage shifting production to the U.S.
What kind of financing has Trump made available so that the average American company (companies of what 5-20 people) can setup multi-hundreds of millions of dollars mining operations, smelters, manufacturing plants? Because it's gonna be a stretch for the average 5-300 person factory around me to vertically integrate into a billion dollars of supply chain infra business.
How much do production workers get paid in China? How will our production goods be affordable at American labor rates? This strategy just makes everything more expensive - nothing cheaper.