The Mueller Report was officially titled "Report on the Investigation into Russian Interference in the 2016 Presidential Election".
You have got things muddled up - the report is in two volumes. You solely quoted from volume 2 regarding obstruction of justice.
Volume I: Russian Interference and Coordination
The special counsel found that Russia did interfere with the election, but “did not find that the Trump campaign, or anyone associated with it, conspired or coordinated with the Russian government in these efforts, despite multiple efforts from Russian-affiliated individuals to assist the Trump campaign.”
Volume II: Obstruction of Justice
The Mueller report laid out facts on both sides but did not reach a conclusion. Barr’s letter said that “the Special Counsel states that ‘while this report does not conclude that the President committed a crime, it also does not exonerate him.’”