The bill sought to override a change in counting votes for unions in a unionization election. Essentially, the Democrats seek to count a "no" vote as a "no" vote, a "yes" vote as a "yes" vote, and a no-vote as a no-vote. The Republican position is that no-votes (i.e., not voting at all) should count as a "no" vote, the same as actually, you know, voting "no."
Between that and the fight about funding rural airport support, which favors Democrats (among them, Harry Reid), makes for a contentious time. But instead of funding, say, two months of operation, while Congress fights it out, the Republican House simply went home. At a cost of some astronomical amount per week, putting construction projects on hold and ending the collection of ticket taxes (and the bloody airlines are keeping the taxes, rather than lowering ticket prices -- one wonders if this is a problem or part of the strategy).
As the whole thing is part of a continuing resolution, there's no reason, other than politics, for doing it this way. It's amazing how good Republicans are at politicking, and how bad at actually governing. Unless someone with money profits, that is.