They weren't a company-specific union but a branch of OPEIU which looks like a general union for what letting agents call "professionals". To translate what I think was happening into British parlance: they were trying to negotiate employer recognition plus a collective bargaining arrangement.

I don't know if their leadership was good or not but American trades unionism is pretty different to ours. Employees typically don't have a huge amount of legal rights and so getting your workplace unionised is much more of a battle than here. On the other hand, America has de facto closed shops which are illegal pretty much everywhere in Europe.