There is no indication of “insufficient evidence” for obstruction.
Mueller Conclusion
“Because we determined not to make a traditional prosecutorial judgment, we did not draw ultimate conclusions about the President's conduct. The evidence we obtained about the President's actions and intent presents difficult issues that would need to be resolved if we were making a traditional prosecutorial judgment. At the same time, if we had confidence after a thorough investigation of the facts that the President clearly did not commit obstruction of justice, we would so state. Based on the facts and the applicable legal standards, we are unable to reach that judgment. Accordingly, while this report does not conclude that the President committed a crime, it also does not exonerate him.”
It was "insufficient" to prosecute or for Congress to investigate. It does not even seem like the Democrats are including those obstruction issues in their impeachment proceedings.
I thought Mueller's report was not what anti-Trump people had hoped for, but I think it largely disproves the whole conspiracy theory for the "deep state" to remove Trump from office. If it had been a plot using phony evidence we would have seen some of it. They would not have conducted that investigation and come up with nothing. Mueller would have at least made some recommendations to prosecute. Such an elaborate conspiracy would have found some evidence even if they had to manufacture it.