Voters with college degrees tend to be more concentrated in Democratic fields. Fields such as Education, Medicine, Journalism, Law, social sciences and Tech often lean left. While many fields that do not have as much of a requirement for university education such as mining, oil/natural gas,construction, and agriculture tend to lean right. Trump also made major inroads into the manufacturing sector which also tends to have less of a requirement for a university degree.
Paul Wells wrote about this in "Right Side Up", is book about Stephen Harper's rise to power.
Much larger swathes of the educated have economic incentives aligned with larger government (e.g. workers in not for profits, education and healthcare) compared to the past. Meanwhile many less educated workers have had their incentives line up with the economic right in ways they wouldn't have in the 1950's (e.g. workers in mining, oil and gas etc). This has diluted the economic left (since fairly well off, educated folks aren't going to vote for radical change even if they aren't conservative), and forced the right to "downscale" their coalition.
His argument is slightly dated as it was written before the recent upswing in right wing populism, but it still explains part of the appeal of Trump and shifting GOP/Dem coalitions.
