I don't think we can rule out the possibility we don't actually know what the employees truly think because they're in the middle of an all out propaganda war.
And I certainly don't think Amazon would put so much effort into fighting this if their employee treatment, benefits and compensation and general employer track record made employees genuinely not even consider the Union option.
As an outsider, it just feels like watching media reporting a war. I don't trust it due to propaganda and clearly opposing biases at play between the interested parties.