But, collective bargaining is only a single aspect of unions. They're not voting against it because they dislike collective bargaining, but because of other reasons. Collective bargaining is likely not a significant motivator for them because their salaries really are fairly high for the area.
I think in many cases unions are good, and in many others they are bad. I disagree that you can point at overall data and use that decide a specific case. Union data likely has severe survivorship bias, since unions likely tend to exist where they are more helpful.
I don’t see how a propaganda campaign can push the vote to 70%, this is not Soviet Russia. Money does help but not on this order of magnitude (see Mike Bloomberg or many failed ballot propositions with tons of money behind them).
Pro-union people have a lot of work to do to restore the reputation of unions more generally. We need to up our propaganda game a lot because we got crushed in the Reagan era and never recovered.
Why can't you just leave them alone?
The unions asked them if they wanted to unionise. They said 'no thanks'. Why isn't that enough for you? If you support workers' right to have a voice then listen to them when they use it. Some individuals are even quoted in the article - they want the unions to leave them in peace!
I don't know your life experiences but I think you've got a funny idea that unions are some kind of perfect good descended from heaven? In reality in most cases unions come with a lot of unpleasant people and politics and aggravation. The workers are already seeing that aggravation with all this unwanted attention. That's one extra problem than they had before, and they don't have any confidence the union will reduce any problems they already had. And the union wants to be paid hundreds of dollars a month for the privilege! What a joke and no wonder people are hostile. I bet people are going to be even more hostile at the next factory these unions turn up at.
From the workers' perspective, there is an endless supply of people who will offer to take their money or the little power they have in return for supposedly 'fighting to improve their lives'.
Most of them do not really share your interests, and many are actively trying to trick you to use your money and power for themselves.
See for example the majority of politicians.
So far this union has uninvitedly hassled these workers for months, and then reacted angrily when they said 'no thanks' in a vote, so I can understand the workers are not buying now even if they were considering it before!
Not all of them will be able to deliver.
Not all of them were genuinely interested in you or your problems in the first place.