When did the labor movement turn against its workers? I don't know that one can name a fixed date, but there was a tipping point during my lifetime where the old concerns of wages, working conditions and societal health became secondary to unrelated cultural issues.
Indeed, the very values of working people became anathema to the leaders of the movement founded to help them.
Concurrently, the conservative movement - which had emphasized those cultural and religious concerns - was more interesting in maximizing corporate profit than anything else.
The Dobbs decision was particularly illuminating in the latter respect. It was a triumph of justice nearly 50 years in the making, yet many alleged conservatives issues statements that could have been written by Planned Parenthood donors (not that we can rule that out). Some said nothing, which also spoke volumes.
A while ago I noted that the American right had decided that maximizing profit was not a question of business practices but instate a sacred duty. Paying American workers five times what Mexican workers would take as an affront to the God of Economics and this injustice could not be allowed to stand.
I think there was more than a little Calvinism in this calculation, as evidenced by the callous "learn to code" advice given to displaced factory workers. The resulting family collapse and drug abuse were clearly a sign that these people were morally questionable and obviously not destined for salvation.
To be far, unions brought much of this on themselves through corruption and betrayal of their workers' interests. There's an understandable progression from endorsing a party for its economic policies and then embracing its social ones as well, regardless of what the membership feels about it.
As in any agreement, once one side realizes that it can alter the terms at will without consequences, everything is on the table.
When that happens, the reason for membership evaporates, and thus former labor strongholds transform into right to work states.
Concerns about working conditions and the concentration of wealth are not new and they have arguably gotten worse over the last three decades. Much of the turmoil in American politics in particular is coming from the collapse of the prior relationship between blue collar workers and the various political factions.
In a lot of ways, the old Labour Parties resemble the established churches where they were born - they wear the same vestments, use the same symbols of a century ago, but they've transformed their doctrine into the opposite of what they once believed.