The lower, White middle class had it made with good paying factory jobs following WWII. Then the bottom fell out when foreign competition reemerged.

Thus many White Americans became what a social critic of the middle of the last century, Eric Hoffer, called the new poor. Because the good times are fresh in the mind of the new poor, they form the most restless and destabilizing segments of the social order. This we have gotten crazy Trump from their frustration.