The reason Trumps idea appeals to people for those unaware is that free trade destroyed a lot of union jobs, which were outsourced to emerging markets. After the industrial revolution unions fought for worker rights and salaries, and they were shipped away to places that didnt have those rights, and they see this as a reversal of this.

Not sure if its right or wrong, but you cant fault them for holding out hope. Its actually a left wing ideal in a way.