This isn't anything new. Conservatives have been blaming Obama for leaving Iran too early since 2010.
I think there's something to this argument- namely that, before they left, Obsma could have pressured the Shia government to do something to alleviate the plight of the Sunnis. That was talked about but didn't happen. Hillary suggested it but was overruled, so Ive read. If that's true then she doesn't deserve blame for this IMO. But Obama does. And he and Hillary both are responsible for arming all Syrian Rebels indiscriminately, and helping ISIS that way.The person most responsible for ISIS is George W Bush. But a little of the blame, just a little, goes to Obama and Hillary.