Who are the ostensibly secular rebels? Every rebel group seems to have propaganda videos on YouTube except the 'secular' ones. Call me sceptical. The only secular group we know of for sure is the Syrian National Army but Assad is their leader and he has been labeled Official Bad Guy Who Must Go. (Just prior to the war HRC said she considers the Assads "close friends".) Hmmm.... Former US pal Sadaam (secular despot) and the secular despot Gadaffi had "to go" too and look what that did.
At any rate, the 'secular' fighters are now more often called 'moderate' rebels. Hell, Al Queda (fighting in Syria as the Al-Nusra Front) is moderate compared to Daesh. Since 2012 they and other 'moderate' Islamist groups received funding and weapons from the US, UK, France, Israel, the Gulf States, Saudi Arabia. Many of the arms ended up in Daesh's hands anyway. One doesn't hear a lot about the, at one point much lauded, Free Syrian Army except that many in their ranks have defected to Daesh.
The stuff I mentioned above is as close to factual as it gets in this chaotic war. The information comes from so-called reliable media sources with supporting documents provided. This doesn't guarantee absolute truth of course.
It's interesting how almost every person has strong opinions about the clusterfuck unfolding in Syria/Iraq and the role Daesh plays in it, but very few of those people actually have enough trustworthy information to make an informed opinion. The fog of war and the spread of disinformation, and just plain old misinformation, is as relevant here as in any other war.
It doesn't help that Senator McCain advocated supplying Daesh with weapons to shoot down Russian fighter aircraft and even had his picture taken posing with Daesh. The US and its allies and lackeys have a rich history supporting and arming extremely vile regimes and insurgent groups when it serves their interests.
The West provided the fertile soil from which Daesh sprouted and now the chickens have come to roost. Big time.