He also didn't conclude that Trump had committed a crime as you point out. If the point wasn't to investigate and determine if a crime had occurred or not then what was the point?
I think it is very important to understand that the Special Council investigation wasn't focused on Donald Trump.
It wasn't an investigation into whether Donald Trump had committed crimes.
But it is a valid question. Why investigate the president at all if you aren't going to conclude that he committed a crime?
In Mueller's statement to the press he addressed this.
Answer:
"First, the opinion explicitly permits the investigation of a sitting President because it is important to preserve evidence while memories are fresh and documents are available. Among other things, that evidence could be used if there were co-conspirators who could now be charged."
So it is to catch co-conspirators, and it preserves evidence, supposedly which can be used once the President is no longer in office. It could also be used by Congress to remove the president from office as a non Justice Department process.
Was the point to say 'we couldn't exonerate?" I don't think that was the mandate.
They were investigating Russian interference in the USA election and if any person(s) in the Trump campaign collaborated with the Russians in their attempts to interfere.
I think they would have liked to have exonerated the president if the could. It would be better for the country to have confidence in their president.
But it does speak volumes for them to explicitly state that they could not exonerate him. Why even state that? We know they couldn't claim that he is guilty of something, so it does seem that they are giving strong hints that the evidence presented needs to be seriously considered and assessed as to whether it meets the criteria of a crime.
The mandate was for him to find wrong doing including if Trump cooperated, collaborated etc with the Russians.
The mandate wasn't about Trump.
It was about the Russians and the Trump campain.
And Mueller dis not present any evidence of a crime
Mueller did document the evidence, it is in the report.
nor did he state he believed a crime had been committed.
Mueller, explained why the SC didn't assess if Trump himself committed a crime.