Unions are commie from the get-go.
Your history is wrong. Unions evolved from the craftsman/apprentice tradition of the 16th to 18th centuries. In the 19th century, because of employer abuse of labor, they were organized to give labor power to negotiate with employers. Early unions were not ideological. In fact, they were very pro America. I can recall NYC hardhats wearing American flag decals on their head gear in the 70s. The were very antiCommunist and challenged the Vietnam anti-war protesters every day.
Alas, labor has always been fertile ground for Marxists. By the 70s Marxists were pretty much in control of the teacher’s unions. During the Vietnam era there were four ways to avoid military draft service: 1. Flee to Canada. 2. Conscientious Objector. 3. Attend seminary. 4. University education major.
It is not an accident that the anti-war/anti America crowd took those outs. It is also not an accident that education and religious leadership was coopted by the Marxists.
Your claim that unions have always been Marxist is as false as a probusiness friend of mine’s claim that emnployers never abused their employees. If that were true the modern labor movement would never have emerged.