Just a Theory:
Maybe TPTB are using Dr. Muller now as a highly credentialed tool to discredit and eliminate pesky opposing information before it takes hold...and that was the plan all along.
It would follow that his former opinion was underwritten and promoted to tease out all alternate theorists that responded positively to his global warming criticisms by incorporating his findings into their work. Now that TPTB know the players, it is like Lucy and the football (Peanuts comics). They make him yank his former analysis and opinions and reverse his position. His “honesty” and “reputation” now back a popular lie leaving unsuspecting alternate theorists with big new negatives publicly––virtually eliminating them as viable positions because they are based on "so-called" faulty numbers. Dr. Muller may have been unsuspectingly bought and paid for way, way back, as well as the strategy (with or without his consent). It could be that this follows typical form: TPTB maneuvers are done in pieces over time so that they are not obvious or suspected until the final outcome is revealed.
I would like to think that Dr. Muller is unattached to the strategies and is an upright and honest scientist calling it as he sees it. But that doesn’t seem to fit with his suspicion and position (he created a whole project to confront the numbers) to then come to the conclusion that he (validated by the project) was 100% wrong and the numbers were 100% right. It makes more sense that they used him somehow as a pawn to ultimately validate suspected cooked data. The other question is what do the TPTB and the Koch Brothers get out of this...there must be at least one more maneuver in the works. One possibility is that with the latest reversal by Muller, it casts shadow on his other research, namely the cycles, ice age and the companion sun, etc. - the real target? Multiple birds for one stone?
Just a theory and probably flawed, I wasn’t there and I don’t really know.