Mueller isn't a Democrat, and he quite pointedly did not exonerate Trump on obstruction of justice charges. (He also made it clear that contrary to little Donnie's claims, the Russians most certainly did interfere in the election.) Instead, and far from "framing" him, he laid out the case and essentially said, "I can't indict the president, but Congress can take action, so I am leaving it up to Congress."
If you and Donnie don't like that, dear, too bad, but now Congress has a right to pursue this investigation. If Donnie wants to save his presidency, he needs to start acting like a statesman and intelligently cooperate. Otherwise, he will merely be digging a deeper hole for himself.