Puzzle Piece "D": new and, it seems, unmatched, from beg. of Sept 2016.
On Rachel Maddow's show of 06-29-17, she highlighted the then-breaking story from the WSJ, "GOP Operative Sought Clinton Emails From Hackers, Implied a Connection to Flynn"^
The story--from the "GOP Operative", Peter Smith, personal account--basically describes how he assembled a team to locate the hackers who stole the DNC info based on a presumption/hope that the same hackers also stole emails from Clinton's personal home server. If found, he intended to convince them to give them up for use against Clinton.
According to Smith, he believed he was successful in contacting the hackers, whom he also believed were Russian-government-affiliated, but was not convinced that what he got from them were legitimate Clinton emails. So, he called on them to release everything they had to WikiLeaks.
Of course, many documents were released thereafter, but none purporting to be from Clinton's server.
In conjunction with, and throughout, this operation, Smith claimed to be reporting his efforts to ... Michael Flynn.
Puzzle Piece "A": long time piece on the board.
Clinton's emails have been discussed ad nauseum. However, the facts surrounding the deleted ones has rarely been fully explained^^, but it is undeniably true that they were deleted by 3/31/15.
Puzzle Piece "B": on the board since, at latest, 7/22/16.
WikiLeaks releases documents and emails stolen from the DNC sometime in, at the latest, late May, 2016. Russian hackers are believed to be the source of the stolen info.
Puzzle Piece "C": on the board since 7/27/16.
At a news conference, T***p urges the hackers to find Clinton's 30,000 emails and implies they be released to the media.
What is odd about this later-called-joke is that even T***p had earlier referenced Clinton's 30,000 emails as having been "deleted and bleached", and he accused her of doing so in order to avoid turning them over pursuant to a subpoena demand. Recall the "lock her up" chants that were precipitated by T***p's rhetoric that Clinton deliberately deleted the 30,000 emails after she received the subpoena for them.
Why, then, did T***p ask the hackers to "find" and release the "30,000 emails" when he knew them to have been deleted over a year earlier?
Assembling the pieces.
Once T***p got word that the Russian hackings had been going on since, perhaps, as early as mid-2015, and that it was believed others beyond just the DNC had been hacked, T***p imagined that Clinton's emails could have been hacked before they were deleted. He had, earlier, raised the possibility of her having been hacked and, often, repeated that claim as part of his "Clinton can't be trusted with classified documents" rhetoric many times after his find-the-30,000 urging.
As has been amply demonstrated by T***p, himself (birther issue, wire-tapped-by-Obama, millions-of-illegals-voted-all-democratic, biggest-inauguration-audience, etc) once he gets a belief, he maintains it like a bulldog with a bone.
After time for his "belief" to become an obsession, he recruits Flynn to look into how to contact the hackers and get the emails. Flynn, himself, may or may not believe the emails exist, but, being the good soldier^^^, he searches for someone to carry out this task.
Admittedly, a missing puzzle piece, but, somehow, Flynn contacts Smith sometime in August, 2016, and Smith assembles his team. During the search, Smith states that he often communicated with Flynn.
Recall that, often, during T***p's campaign, he and his surrogates seemed "in the lead" on knowing what was coming out of the WikiLeaks releases, always at the ready to attack or defend on the basis of thousands of email entries, all after Smith made contact with hackers who had the documents leaked to WikiLeaks.
T***p and/or his campaign may or may not have, initially, colluded with the Russian hackers, but once the campaign became aware of the hackings and leaks, they did their best to take advantage of the situation, including, attempting to be complicit in the theft and dissemination of private documents.
^^Deleted emails timeline:
Dec.2014: aide to Clinton tells an employee of the company that managed her server to delete emails on Clinton's server, unrelated to government work, that were older than 60 days. That employee failed to do so.
3/25 to 3/31/15(unclear exact date): the employee realizes he did not delete the emails as requested. The employee deletes the emails using a program called BleachBit.
^^^With all due respect for what Flynn had done before leaving the military, no one knowing Flynn and commenting on his abilities believes that Flynn would have done anything without T***p's say so, nor is smart enough to have thought up his role, himself.