Yeah that’s not exactly true though. You ever heard of the Battle of Blair Mountain and the Cole Wars?

Overall probably the Kurds.

Certainly not the Salafist and jihadists.

Dude he was fighting the Kurds in Manbij and Efrin with Al-Nusra in like 2016. He founded Al-Nusra, an offshoot of Al-Quaeda, in 2012.

https://www.understandingwar.org/report/jabhat-al-nusra-syria

In January 2012, a group called Jabhat al-Nusra announced itself as al-Qaeda’s Syrian franchise, and the following month al-Qaeda chief Ayman al-Zawahiri called for Sunnis from around the region to join a jihad against the regime. Jabhat al-Nusra gained Syrian and foreign recruits as it scored greater battlefield successes than rival opposition groups.

In April 2013, a separate group formed from the remnants of al-Qaeda in Iraq that called itself the Islamic State of Iraq emerged and exceeded even Jabhat al-Nusra in its brutality

https://www.cfr.org/article/syrias-civil-war

https://en.wikipedia.org/wiki/Battle_of_Ras_al-Ayn_(2012–13)