All employers are making their case at all times, throughout hiring, with pay rate consistency or discrepancy, communication, management, and culture. Union votes are an outcome of the case an employer has already made for themselves. Once the vote's on, it's going to be very difficult to refute the case they've been making for years.
Taking ownership of the failures that led to the conditions which created support for the union vote in a substantial, committed, and convincing fashion is hard, but potentially an effective way for employers to change the direction of the case they've made to employees.
Directly instructing employees to vote "no", lying about how unions work in their area, lying about the voting timeline, installing an easily surveillable special mailbox for union votes, and pressuring the government to alter traffic controls to prevent employees from being able to spend time outside the workplace during the union voting period - this is how Amazon has chosen to make their case.