As others have stated, the report only lays out the evidence, it DOES NOT give a recommendation on indictment or not based on that evidence.
There are clear examples of obstruction of justice in the report, which is a crime. If you read the wording in the report and his careful statements you will realize that the report is not meant to lay out charges, only evidence.
In fact he EXPLICITLY said that the report does NOT exonerate Trump.
The report or the SC was never tasked to exonerate/not exonerate anyone. Mueller was tasked to investigate and provide back a determination/recommendation. Report:
"Accordingly, while this report does not conclude that the President committed a crime, it also does not exonerate him."
"Third, we considered whether to evaluate the conduct we investigated under the Justice
Manual standards governing prosecution and declination decisions, but we determined not to apply
an approach that could potentially result in a judgment that the President committed crimes. The
threshold step under the Justice Manual standards is to assess whether a person's conduct
"constitutes a federal offense." U.S. Dep't of Justice, Justice Manual§ 9-27.220 (2018) (Justice
Manual). Fairness concerns counseled against potentially reaching that judgment when no charges
can be brought. The ordinary means for an individual to respond to an accusation is through a
speedy and public trial, with all the procedural protections that surround a criminal case. An
individual who believes he was wrongly accused can use that process to seek to clear his name. In
contrast , a prosecutor's judgment that crimes were committed, but that no charges will be brought ,
affords no such adversarial opportunity for public name-clearing before an impartial adjudicator .5
The concerns about the fairness of such a determination would be heightened in the case
of a sitting President, where a federal prosecutor's accusation of a crime, even in an internal report ,
could carry consequences that extend beyond the realm of criminal justice. OLC noted similar
concerns about sealed indictments. Even if an indictment were sealed during the President's term ,
OLC reasoned, "it would be very difficult to preserve [an indictment 's] secrecy, " and if an
indictment became public, "[t]he stigma and opprobrium" could imperil the President's ability to
govern." 6 Although a prosecutor's internal report would not represent a formal public accusation
akin to an indictment, the possibility of the report 's public disclosure and the absence of a neutral
adjudicatory forum to review its findings counseled against potentially determining "that the
person's conduct constitutes a federal offense ." Justice Manual § 9-27.220."
https://www.cnn.com/2019/04/18/politics/full-mueller-report-pdf/index.html