"The problem is simply that the effort to build an opposition the west could associate with and that could hold its own on the ground has come up empty"
There is nothing 'simple' here except ridiculous statements like that one. A more accurate, and more truthful, description would be:
The effort to build an opposition the west could associate with and that could hold its own on the ground: has repeated the same pattern we have seen for decades: - arming groups of fighters who hate the US more than they hate the 'enemy'. Fighters who subsequently use those weapons to kill allied soldiers and the people we are supposedly trying to protect.
In summary, US policy in Syria, as in Libya and Somalia, has destabilised these regions and left increasingly extreme and murderous jihadis in charge. Western efforts have not come 'come up empty' Mr Haas, they have come up full of poison.