There were tons of evidence that Trump and his people colluded (and obstructed justice) but Mueller decided it was not wise to press charges.
Not exactly: the special councel's office followed a longstanding Department of Justice legal opinion that a president is temporarily immune to criminal prosecution for the duration of his term in office.
The
"Mueller Report" stated that neither Trump himself nor anyone associated with his campaign participated in a criminal conspiracy with the Russian operatives who were interfering with the 2016 election. The report presented considerable evidence that persons close to Trump
colluded with the Russian operation, but there is no federal crime of "collusion" and the lawyers on the special counsel's staff apparently concluded that the behavior of Trump's associates (including some members of his family) was not sufficient to meet the requirements of a successful conspiracy prosecution.
Note that only Trump was temporarily immune to criminal prosecution; if the special counsel's office believed some of his associates had participated in a criminal conspiracy, they could have been prosecuted under the Justice Department policy. So I read their decision as an exoneration on the criminal conspiracy theory.
The report offered evidence that was more than sufficient to establish a
prima facie case that Trump himself had obstructed Justice by interfering with the counterespionage investigation into Russian interference with the election and, but for the Justice Department policy, he presumably would have been prosecuted. Technically, he still could be, but I suspect the current attorney general, Merrick Garland, would be prepared to violate his own promise to Congress not to interfere with prosecutorial decisions if one or more of the regional U.S. attorneys attempted to bring obstruction of justice charges against the former president—on the theory that it is important to make it clear that the Department of Justice no longer is engaging in the politically-motivated behavior of Trump and his attorneys general, even if that meant forgoing a prosecution that had a good chance of resulting in a conviction.