The facts were that there was no provable criminal conspiracy with Russia. That doesn't mean they didn't collaborate with Russia. Some of the actions taken by Trump's campaign, such as the meeting in Trump tower, were illegal, but, just as in Hillary's case, Mueller didn't believe he could prove criminal intent beyond a reasonable doubt.
From the Mueller Report:
"The Office considered whether to charge Trump Campaign officials with crimes in connection with the June 9 meeting described in Volume I, Section IV.A.5, supra. The Office concluded that, in light of the government's substantial burden of proof on issues of intent ("knowing" and "willful"), and the difficulty of establishing the value of the offered information, criminal charges would not meet the Justice Manual standard that "the admissible evidence will probably be sufficient to obtain and sustain a conviction." Justice Manual§ 9-27.220.
In brief, the key facts are that, on June 3, 2016, Robert Goldstone emailed Donald Trump Jr., to pass along from Emin and Aras Agalarov an "offer" from Russia's "Crown prosecutor" to "the Trump campaign" of "official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to [Trump Jr. 's] father." The email described this as "very high level and sensitive information" that is "part of Russia and its government's support to Mr. Trump-helped along by Aras and Emin." Trump Jr. responded: "if it's what you say I love it especially later in the summer." Trump Jr. and Emin Agalarov had follow-up conversations and, within days, scheduled a meeting with Russian representatives that was attended by Trump Jr., Manafort, and Kushner. The communications setting up the meeting and the attendance by high-level Campaign representatives support an inference that the Campaign anticipated receiving derogatory documents and information from official Russian sources that could assist candidate Trump's electoral prospects.
This series of events could implicate the federal election-law ban on contributions and donations by foreign nationals, 52 U.S.C. § 3012 l(a)(l )(A). Specifically, Goldstone passed along an offer purportedly from a Russian government official to provide "official documents and information" to the Trump Campaign for the purposes of influencing the presidential election. Trump Jr. appears to have accepted that offer and to have arranged a meeting to receive those materials. Documentary evidence in the form of email chains supports the inference that Kushner and Mana fort were aware of that purpose and attended the June 9 meeting anticipating the receipt of helpful information to the Campaign from Russian sources.
The Office considered whether this evidence would establish a conspiracy to violate the foreign contributions ban, in violation of 18 U.S.C. § 371 ; the solicitation of an illegal foreignsource contribution; or the acceptance or receipt of "an express or implied promise to make a
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[foreign-source] contribution," both in violation of 52 U.S.C. § 3012l(a)(l)(A), (a)(2). There are reasonable arguments that the offered information would constitute a "thing of value" within the meaning of these provisions, but the Office determined that the government would not be likely to obtain and sustain a conviction for two other reasons: first, the Office did not obtain admissible evidence likely to meet the government's burden to prove beyond a reasonable doubt that these individuals acted "willfully," i.e., with general knowledge of the illegality of their conduct; and, second, the government would likely encounter difficulty in proving beyond a reasonable doubt that the value of the promised information exceeded the threshold for a criminal violation, see 52 U.S.C. § 30109(d)(l)(A)(i)."
It's not that the Trump campaign didn't work with Russia, it's that they may not have gotten anything substantial directly from Russia and they were largely unaware of the laws when they were violating them. That being said, given how much Trump and his campaign tried to hide that meeting, including the stated purpose of that meeting, from investigators, shows me that he knew what they were doing was wrong. Moreover, while many of Trump's high level staff were involved, I don't believe it has been proven that Trump, himself, had knowledge about the meeting in real time.