Clearly JV brought him to the race gauging that his form was adequite enough for the win (and with good reason), indicating, in the end, the Tour crash didn't hinder his performance. To the contrary, riding the Tour likely established a base, which, through early exit, could be built upon for the Vuelta. Stage 4 prooved this, but Evenepoel demonstrated to be, in Roglic's own words, "on a different level," till now at least he added pondering Remco's ability to go the distance. Then Evenepoel crashed hard and only for this did he lose some of his advantage in the Sierra Nevadas. Mas surging ahead of Roglic on Serra Nevada prooves Roglic wasn't getting any better, while Remco was still suffering from the effects of the crash.
In July Roglic was needed in support of Vingegaard, the team leader at the biggest race on the calendar, so he remained until unable to contribute to the greater cause. It's harsh, but there are no niceties in pro cycling.