For reasons stated Israel maybe quite happy for Assad to stay. I understand there is a level of push-back from the regime against excessive Iranian influence. How successful that pushback has been or could be in the future - I don't know.
One liners on who is responsible for ISIS don't carry weight any more. ISIS was allowed to evolve over a long period of time dues many layers of stupidity, corruption, ignorance, intransigence, proxy warfare, politicisation of religion and of course people just being fed up with corrupt, sectarian, despotic regimes.
