Why would Russian fighter Jets be in or near Damascus?

Likely the sea Port Assad Gave to Russia which is only one of two warm water ports that don't freeze over in the winter that Russia has. The other port is in Crimea. So, in the end their port in Syria would be more important to them than keeping Assad in power. So, keeping Assad in power is a means to an end.

Also, Russia is as upset at ISIS as the rest of the world is also, especially because many of the Generals and officers of ISIS are Chechen fighters they fought in Chechnya.

Another reason they would be in or near Damascus is Europe, the U.S. and Russia agree on one thing. None of them want ISIS to rule Assad's Syria because it would not only be a bloodbath of Shiites, especially the Alawite Shiites, it would also destabilize countries like Lebanon, Jordan and Turkey which would make life more difficult for millions. So, it is likely by agreement for Russian jet fighters to be there now. However, if it were out in the open many in the Middle East would be upset about this. But, the fact that the U.S. and Europe are silent about this says a lot too. But, for most or all governments in the Middle east there is no desire from likely ANY Middle Eastern Government for ISIS to rule Assad's Syria.