After 8 years and counting for at least one of the three? If your performance is lacking you won't get around to unionizing because your co-workers will see through that ruse in a heartbeat. According to one - insider informed - commenter here about 20% of the company was in favor, not enough to put it to a vote but apparently enough of a reason to ask the company to recognize the union voluntarily. So this was not just a couple of people organizing a union to avoid their own termination.

Why did they want to form a union, after 8 years?

I think some people will always be in favor of a union, no matter what. It's also an ideological thing.