When the unions began losing those elections, they decided to change the rules. And after Barack Obama was elected President of the United States, with large financial support from labor unions, the rules were in fact changed by Obama's NLRB.
As if to make the outcome of workers' "choices" more of a foregone conclusion, the time period between the announcement of an election and the election itself has been shortened by the NLRB.
In other words, the union can spend months, or whatever amount of time it takes, for them to prepare and implement an organizing campaign beforehand -- and then suddenly announce a deadline date for the decision on having or not having a union. The union organizers can launch their full-court press before the employers have time to organize a comparable counter-argument or the workers have time to weigh their decision, while being pressured.
The last thing this process is concerned about is a free choice for workers. The first thing it is concerned about is getting a captive group of union members, whose compulsory dues provide a large sum of money to be spent at the discretion of union bosses, to provide those bosses with both personal perks and political power to wield, on the basis of their ability to pick and choose where to make campaign contributions from the union members' dues.
Union elections do not recur like other elections. They are like some Third World elections: "One man, one vote -- one time." And getting a recognized union unrecognized is an uphill struggle.
But, so long as many people refuse to see the union for what it is, or the Obama administration for what it is, this cynical and corrupt process can continue.