isolated fabio aru

I watched the highlights of yesterdays stage last night. Now by no means do i understand all the nuances of the chess game which is a modern day pro bike race so help me out here. Fabio aru has lost some of his team and the remainder don't seem to be doing much for him so basically if he wanted to remain in yellow he has to box very very clever and go it alone so to speak. Why didn't he take it on himself yesterday to stick to froomey like shit to a blanket all day and pass the finish line with him. Another day done and his 6 second lead intact. Or did he try do this but something happened which distanced himself from froomey which the highlights didn't show.