I was under the impression that Stybar was marking a move for boonen that ended up going away.
Yup, he was certainly doing that. And as such didn’t have to do any work with the lead group (he apparently has said that he was only told he could go for the win at 4km to go – which sounds about right, it wasn’t clear that group would get to the velodrome on their own until about that point). With GvA clearly the strongest rider in the group he had no incentive to do work for GvA, even more so with a viable team mate behind him and by the time he got to 4km to go it was clear that they would make it so why would he waste energy? I think it was poor form of Sean Kelly to criticise him imo.
The big disappointment was Trek-Segafredo’s negative racing. They had the resource (Degenkolb plus two others) and the incentive (no one from their team up the road) to work to pull GvA etc back but showed no desire to do so. If you want to point fingers at anyone for sitting in, that’s where your finger should be pointing.