There are certain products that must be made locally, if not in whole you cant give away the entire industry to globalization. On a strictly economic view this will increase the cost of steal but you have to consider what having no steel manufacturing capabilities in the country means. Indont know how much competition within the country exists for steel manufacturing but if this sale meant no American owned steel manufacturers preventing the sale would be good. I dont know if this specific move would be good but Trump does understand beyond the others that diminishing the manufacturing capabilities could be disastrous for the country as a whole.
You can pay now or you can pay later.