My impression is that the FBI, now Mueller, has significant evidence of wrongdoing related to Russian election interference. They have been gathering evidence for almost a year--some while the interference was ongoing. Enough people leaked enough to keep the investigation going. We can now expect silence.
The new recent public news is that actual human Russian spies with tech skills were operating in our country. Some Russians with technical skill tried to follow them and were denied entry. We apparently knew about the human spies last summer and fall, and the FBI likely was watching them during their period of interfering. They were among the Russians expelled.
It now seems that in addition to electronic interference from abroad, there were actual humans conducting operations here. They were presumably in the country in order to be in contact with, or actively work with, Americans. This effort would need lots of money for bribes and it had to be moved around, probably illegally. This leaves tracks, in the US, involving Americans in legal peril (as opposed to Russians and Macedonians).
Yates testified that Flynn's underlying conduct on December 29 was problematic. We know that he discussed sanctions relief. I have believed that it was more since it was 5 calls, from Flynn on vacation outside the US, immediately after Obama expelled the actual Russian spies who did the interference and seized the 2 compounds. We know that the Obama admin briefed the Trump folks at the last possible moment about this expulsion and seizure. "We are going to be nicer to you" does not take 5 telephone calls. Before I understood that there were actual Russian agents with tech skills incountry, I wondered if the extra calls were Flynn negotiating his pay off for being nicer to the Russians. There is now potential that they were discussing what Flynn had found out about what we knew about the expelled Russian agents--and maybe a plan to cover up some tracks. The unexpected expulsions may have pressured Flynn into a higher degree of recklessness (i.e. talking on a phone line which was likely monitored).
The skill set of Mueller's team includes tracking illegal money, interrogating Russians, flipping witnesses, and bringing a complex prosecution. The probabilities of prosecutions that change public opinion increase if there were actual Russian citizens (under surveillance) taking actions to disrupt our election in favor of Trump. They likely left evidence and we get to something that changes public opinion if Trump campaign officials and other Republicans were involved in helping them, or in covering their tracks.