Luther IMO and as a bottom line at that stage João was not at his best and sure we can speculate about what was behind it... for me the simple explanation is usually the right one, so...
- maybe he was in the wrong mood feeling that DQ was protecting Remco and neglecting him
- maybe he couldn't cope with the weather
- maybe he forgot to eat when he must to
At the end he was not good enough, had a bad day, as all the other riders had at some point in their careers and it was his fault, no one else. He is with the big boys now, so he must acting like one if he wants to succeed.
Despite all that DQ did a lot of bad calls for this Giro, that is a certainty by now