As a result of obstructive efforts and other practical obstacles, Mueller’s team was unable to complete many of their intended investigative steps.
www.justsecurity.org
"Mueller wrote: “the investigation established that several individuals affiliated with the Trump Campaign lied to the Office, and to Congress, about their interactions with Russian-affiliated individuals and related matters.
Those lies materially impaired the investigation of Russian election interference.”
Mueller found “substantial evidence” to support multiple counts of obstruction of justice, including 10 episodes involving President Donald Trump interfering with the investigation.
Mueller also noted that former campaign chairman Paul Manafort “lied to the Office and the grand jury concerning his interactions and communications with Konstantin Kilimnik about Trump Campaign polling data and a peace plan for Ukraine.” According to the Mueller report, the FBI assessed that Kilimnik has “ties to Russian intelligence.” Manafort’s lies about providing polling data prevented Mueller from fully understanding the purpose of delivering the information to Kilimnik."
And trump would not talk.
Read the second half of the Mueller report. It's all about obstruction.
Stop trying to fool the weak minded with your revision of history.