> All he (or anyone) can do is interpret or analyse poll results, and then surface their findings in a way a larger audience can understand.

He (or anybody) can make adjustments to the data. He was challenged to explain why his predictions were so different, but he wouldn't do it.

> 538 did that better than any other poll analyst

He made a binary prediction, and it was wrong. There's no such thing as "better" when you only have one outcome. Your prediction is either right or wrong. If by "better" you mean he was wrong but assigned a higher probability to a Trump victory, the best forecaster would have been someone that mechanically changed the probability of a Trump victory to slightly less than 50% no matter what the data said.