It's not just Trump, and it's not just a single election.
No, they've been losing ground pretty steadily for 20 years. The media didn't pay much attention until recently because most of the losses were occurring in "flyover" areas.
They're paying attention now.
Even at the Federal level, the Republicans have had control of the House of Representatives since 2010, and the Senate since 2014.
And I don't agree that it's just the U.S. In other countries you have Brexit, the rise of the Le Pen family in France, etc.
I'll go first, I think that is mostly because of a disastrous 2010 off-year election, its ensuing redistricting period, and, well, I enjoyed this piece:
http://fusion.net/the-long-lucrative-right-wing-grift-is-blo...
Utter failure of the current Democratic Party to connect with those voters who made up its base for a century or more.
I don't think there's any other way to spin it. Trump won because he carried several industrial and mining states that were traditionally Democratic strongholds.
Your link is just another attempt to blame it on "stupid racists".
Did it ever occur to the Dem leadership that calling people stupid racists doesn't make them more likely to vote for you?
Those states all voted for Obama twice. While I suppose it's possible that everyone in those states turned into a stupid racist over the last four years, that's not where I'd place my bet.