It all started back when Kagan was nominated to replace Stevens, the feeling in some circles in DC was a janitor was more qualified to fill that seat than she was (and they were right). So sensing he might have problems getting her confirmed Reid threatened to use the nuclear option to get it done. But that wasn't needed because some of the usual swamp creatures in the Republican party crossed over and voted for her (
Richard Lugar, Lindsey Graham, Judd Gregg, Olympia Snowe, and Susan Collins). So it was placed on the back burner until 2013 when he finally decided to use it to pack the DC Court of Appeals with more unqualified activists.
The Dems also hatched this crazy plan to use it to get Garland confirmed in the time between the 114th Congress ending and the 115th Congress beginning when there would be a Democrat majority for a short period of time. Needless to say someone sane realized the plan would be illegal and so it died a wheezing death.