The CIA and Israel are responsible for the creation of Isis. Isis was created specifically to weaken Iran and destabilize Syria. It worked for awhile until Putin shored up Assad and bolstered Iranian Qud forces. The real reason you see such anti-Russian fever from both Schumer and McCain, Graham and Feinstein, is because the operation has blown up in our faces.
Certainly, there is no satisfactory official explanation why we are spending billions to bring down Assad.
Let's go with this until a better one is offered.
 DHS Insider quoted in "DHS Insider: Pedogate Exposes CIA-Mossad Deep State." By Henry Makow, henrymakow.com, 2/17/17.