Any non-state entity exists at the blessing of one or more state entities with power, money, and help.

The "fact" that this question is never asked by "news" organs is very telling. It is a very hot topic on the other side of the geopolitical fence, this patron of ISIS ..

Why, we can all count fingers on one hand, can't we? We know whose proxy they ain't and after that it is process of what is not eliminated. Some say they are the original counter-counter-proxy (cause the others also liked the idea of this genre and made counter-proxies) and with the first proxies (in that genre) being the Mujahidin in Afghanistan hitting USSR troops, unless you want to go all the way back to Lawrence of Arabia and Ottomans ..

p.s. part of the deal Nixon made with Mao was that CPC would no longer support various cells in the 'Global Energy Zone' since they were now "partners" in the Global Economy. Overnight thousands of Maoist flowers all over campuses and in middle east went away. All these groups existentially require a powerful patron or two. So ISIS has a mommy and a daddy and it aint Russia and it aint Iran and China has been out of that game since 70s as a matter of historic fact. That leave US, UK ("the Empire"), the Europeans (French? Doubtful), and Israel, KSA, Qatar and UAE. Qatar is Muslim Brotherhood [& so is Turkey] so that seems to eliminate it [them]. That basically leaves Western and Abrahamic patriarch wanna-bes at the table of candidates.

The CIAs.