Quneitra , Deraa and Suweida province have been closely contested the last few months. The Israelis have been flying Close Air Support for their favorite flavors of jihadi rebels in the area close to the Golan Heights (occupied Syria). They have also been providing medical evacuation and support for the same. Why? they seem to think that a jihadi controlled buffer zone between them and Damascus is better for them than Syrian government control. They do this in spite of the factoid that until the civil war began in Syria, there had been quiet along the front there for a long time.
The Israelis are unable to cope with the missile and artillery rocket threat from Hizbullah north of the present front line north of the present line of contact. They know that. Neither air attacks or a possible massive Israeli ground attack into Lebanon would prevent HB firing a lot of their arsenal (30,000 weapons) into the northern half of Israel. Their belief is that if they take down the Syrian government they can achieve an operational level envelopment of Hizbullah's firing positions in Lebanon. They also believe that defeat of the SAG would fatally wound the Iranian government politically. None of that seems very likely to me but the scheme fits well with US enmity toward the Syrian government. Perhaps an eventual offensive toward Damascus is dreamt of in DC (certain circles). That doesn't seem very likely to me either.
The prospect of such a cease fire must seem a good thing to the SAG. The SAA (R+6) are perennially short of troops. A massive (for them) offensive in the east is imminent. The objective will be the extermination of IS from eastern Syria and the relief of the long besieged Euphrates River city of deir al zor. A temporary reduction of the level of commitment to the SW would be helpful.
Why did Trump and Tillerson agree to this "deal?" I doubt that they understand the military situation and Kushner was not in the room to argue for the Israeli interest. pl