The factory isn't even being "filled with foreign workers", it's being set up by foreign workers so they can start employing 10x as many locals to actually staff it long term.
At the time it was actually filled with foreign workers, who were likely here illegally. Look, I am no fan of trump or any of what ICE is doing, but the fact is there were 300 foreign workers here illegally inside that factory. That's completely stupid of the company to do considering the current political climate.