In retrospective, likely the tension started to build up on stage 6. Realization, they are not good enough, as a team. That getting confirmed on stage 8, and due to Dumoulin stepping up, for that to paid off in stage 9. The situation wouldn't improve by itself. Something needed to be done. Ignoring the indicators, late into week 2, that would likely end up being a bad call.
Dumoulin likely always knew, if it will be his time to pull, he will do that. And realistically, that already happened in week 1. His time came and JV could pull off Movistar, or deliver. Dumoulin decided, heck, lets deliver. Lets win it then, i can go after a stage win, be a part of the winning team ... Still heaps better, compared to where i was not that long ago.