This is why it's being brought up now.
https://www.washingtonpost.com/technology/2021/04/08/amazon-bessemer-mailbox-union/
"The union trying to organize workers at an Amazon warehouse in Bessemer, Ala., sounded a pessimistic note Thursday as a partial tally showed votes against the union with an early and widening lead.
With about half the 3,215 ballots counted, no votes hit 1,100 while yes votes totaled 463. The count was scheduled to resume on Friday.
“Our system is broken,” Retail, Wholesale and Department Store Union President Stuart Appelbaum said in a statement Thursday night that seemed to anticipate defeat. “Amazon took full advantage of that, and we will be calling on the labor board to hold Amazon accountable for its illegal and egregious behavior during the campaign” — a reference to the National Labor Relations Board, which is overseeing the vote.
One area on which the union probably will focus: Emails among U.S. Postal Service employees in January and February show that Amazon pressed the agency to install a mailbox outside the warehouse, a move the union contends is a violation of labor laws."
Edit: Also at CNN if you'd prefer a non-Bezos owned source:
In most situations, a mailbox is just a mailbox. But in the milestone union election at an Amazon warehouse in Bessemer, Alabama, a mailbox installed earlier this year threatens to upend the whole process -- or at least become a focus for the union if it loses the vote. The public tally began...
www.cnn.com
"According to the union, the NLRB received 3,215 ballots. When the NLRB stopped counting votes for the evening, the votes
were heavily in Amazon's favor, with 1,101 voting against the union and 463 in support. In this election, nearly 6,000 warehouse workers at the
one-year-old Bessemer facility were eligible to vote. The count will resume Friday morning."