It's not necessarily anti-trade, it's anti-status-quo.  The trade deals as negotiated in western societies today has a flaw that automatically whittles down the manufacturing base.

If anyone doubts that there is massive economic inequality and under employment in the US, look at the comparison between 2000 and 2014,  it showed that while average income had grown, median income had fallen 8%.  Behind that fall in median income, the rust belt --- the manufacturing base (brexit states) saw large portions of the US population fall out of middle class life.  

Another reason why Trump touched a nerve in the flyover country is that labor participation rate is at a historic low never seen since the days of Carter.  There's a large number of people that are not counted in the unemployment rate numbers.

Then there's the obamacare premiums increase.

There was always a core that wanted to punish the elites, but the rest came from the results of sloppy leadership in the US,