Option 1 is literally false. If you look at the heavily black precincts in Milwaukee, turnout actually went DOWN from 2016, in addition to Trump doing slightly better than in 2016. You find this in some heavily black urban areas across the midwest as well. But, turnout went up enough in the white areas of the city and county for it to not be noticeable on a county level.
Most of Trump's defeat can be explained the same way it can in other states. Rich, college-educated suburbanites fleeing him in droves worse than in 2016 and R's in 2018. These are people who are traditional/habitual Republican voters who likely held their nose in 2016, but couldn't tolerate him once in office. If it were really about the tariffs broadly and not in select individual cases hurting farmers, you'd see more rural bounceback, but in fact you saw rural areas in Wisconsin swing slightly more towards Trump vs 2016.
This is right Milwaukee's black population has been going down in recent years either moving to the Chicago area or more generally the south in droves.