Most of the relevant fighting on the rebel side of the Syrian war has been done by the Nusra Front, and the similarly Al Qaeda minded Ahrar al Sham and Jaish al Islam, not to mention many other Al Qaeda or IS splinter groups including Chechen, North African or other Central Asian fighters.
The remnants of the so called „moderates“ have almost never hesitated to work closely with Al Nusra or even IS when it deemed necessary. Therefore all the occasional „bond breakings“ of the so called „Southern Front“ with Al Nusra cannot be taken seriously. One day they announce to have broken all ties with Nusra and opposing them, but when the Syrian army captures two villages they call for Nusra to help.

Now, nobody but extremely naive people believes that the radical and mostly sectarian islamists who bore the brunt of the fighting will lay down their weapons and quit the political field once Assad is defeated and gone/killed. These people have never fought for anything remotely resembling a „western“ civil state with democratic institutions and human rights implementation. Those who demonstrated against Assad will find out (just as Iranians post 1979 and Libyans after Ghaddafi) that what they have gotten is much worse than what they had.
And just like post-Soviet Afghanistan and post-Ghaddafi Libya the many militias will not let anyone disarm them.

The failure in Iraq was „explained“ with the Shia-Sunni conflict, but where are the Shia in Egypt? How many Shias live in Libya? Are the Afghan Shia a relevant force to claim that Taliban enjoy support to „counter balance“ them?
I know that Arab leaders and media are very creative in connecting Iran with any problem in their countries but is Iran „meddling“ in Egypt or Libya? Is Boko Haram in Nigeria or al Shabab in Somalia a „reaction“ to „Iranian expansionism“? Are takfiri groups in Kashmir or in Pakistan suffering from Iranian or „Shia oppression“?

Only complete idiots claim that with the departure of Assad and the victory of the „revolution“ peace and prosperity will return and prevail. Just see how Afghanistan fares, 14 years after „liberation“, after the mission being „accomplished“. And just judge for yourself whether Al Qaeda has been weakened after 14 years of the (seemingly endless) „war on terror“, after killing Bin Laden and after drone assassinations of dozens of Al Qaeda „top commanders“ in Africa, Iraq, Yemen, Afghanistan and Pakistan.