The National Labor Relations Act prohibits employers from firing employees for participating in union activities.
I don’t believe they were a part of forming or attempting to form the union, but we’re the management of the facility. Maybe I misread it. Maybe they have a claim because it’s highly likely they were let go because they did squash the attempts at forming a union?
Is it really illegal to fire managers who failed to prevent unionization of the employees? Because that is what seems to have happened here.
It's not, supervisors are excluded from union organizing protections.
These employees were management. They are explicitly excluded from union activities because they represent the company.