My take - Rubio was wanting to use it in the event he made some kind of showing in Florida, but that didn't happen.
I don't think Rubio had anything to do with it's release now, either. Anonymous threatened to release evidence days before the NE ran with it, and NE not only already knew about the story, they had also had time to investigate it further to see if anything panned out.
I think Rubio is planning a come back at convention.