Hell, yes, there was collusion!

Collude: ": to work together secretly especially in order to do something illegal or dishonest : CONSPIRE, PLOT"

ASSERTION
It is beyond all reasonable doubt that the Trump campaign colluded with the Russian government by working together secretly to do something illegal (defraud the American people) and dishonest (while denying ANY association with Russians whatsoever).

1. Russia attacked our election: that's illegal.

2. The Trump Campaign, in real time, gratefully accepted Russia's illegal support and planned its press, communications, and messaging around Russia / Wikileaks strategic release of these stolen emails: that's conspiracy.

3. And while this was going on, Donald Trump was telling America that he had nothing to do with Russia. That (as well as his secret, ongoing attempts to close a real estate deal with the Russian government) - to put it mildly - is dishonest.

And whether or not this rises to the level of a criminal conspiracy, it is undeniably collusion as that word is defined in common usage if not in law.

There is only one reason Mueller did not find the Trump campaign's activity actually illegal, per Attorney General Barr's press conference on April 18th, 2019.

"The Special Counsel also investigated whether any member or affiliate of the Trump campaign encouraged or otherwise played a role in these dissemination efforts. Under applicable law, publication of these types of materials would not be criminal unless the publisher also participated in the underlying hacking conspiracy."

Read Attorney General Barr’s remarks on the Mueller report (Washington Post)

EVIDENCE FOR MY ASSERTION

Russia attacks the 2016 election and the Trump Campaign accepts and utilizes Russia's release of stolen emails.

"As set forth in detail in this report, the Special Counsel’s investigation established that Russia interfered in the 2016 presidential election principally through two operations. First, a Russian entity carried out a social media campaign that favored presidential candidate Donald J. Trump and disparaged presidential candidate Hillary Clinton. Second, a Russian intelligence service conducted computer-intrusion operations against entities, employees, and volunteers working on the Clinton Campaign and then released stolen documents. The investigation also identified numerous links between the Russian government and the Trump Campaign. Although the investigation established that the Russian government perceived it would benefit from a Trump presidency and worked to secure that outcome, and that the Campaign expected it would benefit electorally from information stolen and released through Russian efforts, the investigation did not establish that members of the Trump Campaign conspired or coordinated with the Russian government in its election interference activities." 
Mueller, vol 1., p. 1

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"According to Gates [Deputy Campaign Manager, Trump Campaign], by the late summer of 2016, the Trump Campaign was planning a press strategy, a communications campaign, and messaging based on the possible release of Clinton emails by WikiLeaks."  (Source: Gates 4/10/18 302, at 3; Gates 4/11/18 302, at 1-2 (SM-2180998); Gates 10/25/18 302, at 2.)
Mueller, vol. 1, p.54

*   *   *

"On October 3, 2016, WikiLeaks sent another direct message to Trump Jr., asking “you guys” to help disseminate a link alleging candidate Clinton had advocated using a drone to target Julian Assange. Trump Jr. responded that he already “had done so,” and asked, “what’s behind this Wednesday leak I keep reading about?” WikiLeaks did not respond. [Source: 10/3/16 Twitter DMs, @DonaldJTrumpJr & @WikiLeaks.]

"On October 12, 2016, WikiLeaks wrote again that it was “great to see you and your dad talking about our publications. Strongly suggest your dad tweets this link if he mentions us wlsearch.tk.” WikiLeaks wrote that the link would help Trump in “digging through” leaked emails and stated, “we just released Podesta emails Part 4.” (Source: 10/12/16 Twitter DM, @WikiLeaks to @DonaldJTrumpJr.) Two days later, Trump Jr. publicly tweeted the wlsearch.tk link."   (Source: @DonaldJTrumpJr 10/14/16 (6:34 a.m.) Tweet).
Mueller, vol 1, p. 60

Report On The Investigation Into Russian Interference In The 2016 Presidential Election Volume I of II

While the Trump Campaign was doing this they were denying having anything to do with Russia.

"DORAL (CBSMiami) – In his most extensive remarks on allegations that Russia is attempting to influence the presidential election in his favor, Republican nominee Donald Trump flatly denied any ties to the Russian government or Russian investors.

"“I can tell you I think if I came up with that they’d say, ‘Oh, it’s a conspiracy theory, it’s ridiculous,’” Trump told CBS4’s Jim DeFede during an interview at his golf resort in Doral. “I mean I have nothing to do with Russia. I don’t have any jobs in Russia. I’m all over the world but we’re not involved in Russia.”"

CBS4 News Exclusive: Trump Denies Ties To Russia