It is shortsighted of Trump not to take into account other factors besides the trade imbalance.
Trump knows how to negotiate and there are always several things on the table, not just one.
The media did not outright state that Trump was only looking at the trade imbalance. I inferred it from what the posted part of the article implied. If Trump has other rational for putting such a tariff on Lesotho I will gladly be pointed in that direction. For instance to pressure the U.S. companies to stop unfair (or outright abusive) labor practices.