Unionizing takes several steps. First, you have to sign enough interest cards to even begin the process. 30% is about right - you show there's a significant interest in people joining the union. Then you have the certification push - that is, a general vote on if you want to join the union or not. That takes a simple majority - if it fails, then no union. It's basically 30% of people saying they're interested in joining a union.
Thanks for clarifying what TFA did not. The article did seem to indicate the union could start negotiating a contract now. Does that come after being certified?
As for a "monopoly on labor" you have to realize the power mismatch that's going on here.
I get it. That's been the argument for over 100 years. I'm just pointing out that people are inconsistent. Progressives hate monopolies when they are a company using market power to raise prices for consumers (which is actually quite rare) but love unions when they do the exact same thing. The union is sticking it to The Man, woot!
Personally, I dislike any form of monopoly and would prefer the government stopped protecting them, be they businesses or unions. If a union can make a case that it can deliver more and better drivers than randomly hiring drivers off the street, that would be one thing. But it's not, unions don't do anything other than restrict supply.
I think you're right, it's really all about power, not monopolies per se. People feel powerless when up against a large company. In theory, they can vote with their feet or wallet but that just isn't a satisfying answer.