i took "no idea" pretty literally and a wall o text happened. the last paragraph pertains to this thread directly.
a number of trump administration and campaign related people have quit their jobs based on suspicious connections to Russia or because they were caught lying about suspicious connections to Russia in legally-significant ways. Flynn, formerly Trump's national security advisor, is the highest-ranking dude who's done this so far.
The FBI recently confirmed that the Russian government took action to influence the election in trump's favor and that they are carrying out an investigation to determine if anyone from the trump campaign or republican party colluded with Russia on purpose, and who the responsible individuals are.
there's committees in both the house of representatives and senate whose specialty is intel and in theory they should both be investigating this as well. currently, the senate is going full-speed-ahead in a bipartisan manner, while Nunes, an R congressman from California, has more or less brought the house investigation to a stop and is currently doing a tremendous job of seeming like he'll be revealed to be on the list of compromised individuals.
between the Senate investigation and the FBI investigation, it's no longer possible for the Republican party to dismiss this as some Democratic smear campaign. Flynn attempted to cut a deal with the FBI to assist the investigation or future legal case in some way in return for immunity from whatever charges they may want to bring at him in the future. He's been told to take a hike thus far. It seems that the investigators don't believe that he's got anything they need.