Before that meeting with the attorney Donald Trump Jr. received an email stating that the information came from the Russian government which was trying to help his dad get elected.

Courtesy of the New York Times: 

Before arranging a meeting with a Kremlin-connected Russian lawyer he believed would offer him compromising information about Hillary Clinton, Donald Trump Jr. was informed in an email that the material was part of a Russian government effort to aid his father’s candidacy, according to three people with knowledge of the email. 

The email to the younger Mr. Trump was sent by Rob Goldstone, a publicist and former British tabloid reporter who helped broker the June 2016 meeting. In a statement on Sunday, Mr. Trump acknowledged that he was interested in receiving damaging information about Mrs. Clinton, but gave no indication that he thought the lawyer might have been a Kremlin proxy. 

Mr. Goldstone’s message, as described to The New York Times by the three people, indicates that the Russian government was the source of the potentially damaging information. It does not elaborate on the wider effort by Moscow to help the Trump campaign. 

There is no evidence to suggest that the promised damaging information was related to Russian government computer hacking that led to the release of thousands of Democratic National Committee emails. The meeting took place less than a week before it was widely reported that Russian hackers had infiltrated the committee’s servers. 

But the email is likely to be of keen interest to the Justice Department and congressional investigators, who are examining whether any of President Trump’s associates colluded with the Russian government to disrupt last year’s election. American intelligence agencies have determined that the Russian government tried to sway the election in favor of Mr. Trump.

Okay the key phrase here is "before it was widely reported." However it WAS already out there that the DNC was hacked, and in May Crowdstrike had already identified the Russians as the hackers.

Political campaigns are far more focused on this kind of thing than the average American, and that is just setting aside the possibility that the Russians had not already communicated to Trump folks that they had information from those hacks that could help them win.

It was also noted on one of the cable news shows I watched that this meeting seemed to be the catalyst for the hacked information being dumped on the internet.

Only six days later Guccifer 2.0, who has now been identified as a Russian operative, takes credit for the hack and starts dumping internal DNC documents.

And they are followed by Wikileaks which dumps a bunch of hacked DNC info on July 22.

On the 27th Trump senior says this:

“I will tell you this, Russia: If you’re listening, I hope you’re able to find the 30,000 emails that are missing,” Trump said at a news conference. “I think you will probably be rewarded mightily by our press.”

Things then escalated from there.

Of course Trump supporters and Right Wing news outlets are downplaying this as aggressively as possible, with Junior's attorney claiming that it's all much ado about nothing: 

“The meeting lasted about 20-30 minutes, and nothing came of it. His father knew nothing about it. The bottom line is that Don, Jr. did nothing wrong.”

Says the man paid to proclaim his client's innocence despite any evidence to the contrary.

The outside attorneys for Trump Sr. are even trying to suggest that this whole meeting was a Democratic plot.

NEW: spox for POTUS outside legal team casts mtg as part of oppo effort. Source close to team calls it "poss. setup by Russian operatives" pic.twitter.com/1Y145Ooag8

— Hallie Jackson (@HallieJackson) July 9, 2017

I don't even know what to say to that.

The key points here are that Don Jr. KNEW that he was taking this meeting with hopes of receiving damaging information about Hillary Clinton obtained by the Russian government, that was now working to help his father get elected, while there was information circulating out there that the Russians had hacked the DNC.

And he took his father's campaign manager and campaign advisor/son-in-law along for the ride.

And THAT is the clearest evidence of collusion that we have seen thus far.

By the way this is a picture of the guy who set up this meeting on the day after the election.

Rob Goldstone, the Donald Trump Jr. acquaintance who brokered the meeting with a Kremlin-linked lawyer, the day after the 2016 US election: pic.twitter.com/20bMLUvDiH

— Jon Swaine (@jonswaine) July 9, 2017

Take from that what you will.