I believe the correct word to use would be " escape" rather flee. The Syrians who have been liberated from the Al-Queda/Al-Nusra jihadists in east Aleppo are overwhelming pro-government, if any of our media would care to interview them. The jihadists have almost no support in Syria, and that's why they are being defeated. 
It will be interesting to see how many people were actually in east Aleppo. I don't think the figure of 250,000 will prove to be accurate