Reagan was hated by union leadership but admired by many of the rank and file. Trump might be tamping into this. In my experience, the rank and file of most unions are not hostile to a management who is perceived as fair.
When I was in college, I worked summers and breaks at a union sawmill. My father was in management and one summer we had a very contentious negotiation which ended minutes before the strike deadline. Shortly before the settlement, a shop steward pulled me aside and told that me Dad was a hard negotiator but that the union guys liked him because he had never forgotten where he had come from - he had worked himself from common-labor employee to management. One of my favorite memories of my father.
“Reagan was hated by union leadership”
Then how did he get their official endorsement in 1980 and 1984?