Does anyone really believe that the Amazon employees voted against the union because Amazon removed some union material from the break room one day? Of course not. The employees knew what they were voting for and were fully capable of researching it themselves.
The real question is what does the union plan on doing differently to sway the employees to vote differently next time? Repeatedly trying to overrule the employees about their own voted decisions isn't likely to be popular among those who voted against the union, which is most of them. They'll need a better narrative on top of this if they want to get anywhere.
Or alternatively, maybe they don't care so much about this election as they do about making Amazon look bad. Maybe they know these workers don't want to unionize, but they're going to use this opportunity to try to convince the public that the workers were misled by Amazon. If they can't win the workers at this location, maybe they can try to win the public on a wave of anti-Amazon publicity for a do-over in another location.