Some analysts think that this may have all occurred to Russia now as a sort of revenge for Russia not letting the West get its way in Syria.
Putin now has all of this on his doorstep and it may get worse and so he may have to do a deal over Syria in order to solve what could happen in Ukraine.
"The Crises in Ukraine and Syria: Putin Caught in the Jaws of a Vise"
"The Saudis, Jihadis, Al Qaeda etc may be allowed to get their way in Syria, but that is against Russian interests due to the huge gas and oil finds in that region. However, a deal may be found so that Russia's interests in that region can be safeguarded. Russia could not help Serbia when the chips were down, and Syria may go the same way, if Putin does not want lots of trouble in Ukraine.
"Russia did not yet lose all its cards in Ukraine, and will not be on the retreat just yet in Syria, as a result of the setback it suffered in the aftermath of the Ukrainian revolution. Russian President Vladimir Putin's revenge for what happened in Kiev's answer to Tahrir Square while he was preoccupied with the Winter Olympics in Sochi may yet come.
The United States and the European Union are aware of the painful instruments of revenge that Putin has at his disposal, as they are aware of the limits of European economic power and U.S. political power under President Barack Obama. For this reason, Western powers are walking a tightrope in dealing with the developments in Ukraine, all while stressing that this is neither a strategic confrontation nor a return to the Cold War.
For its part, Moscow interprets the events in Ukraine differently, and is suspicious of Western intentions there. However, Moscow also recognizes that resorting to revenge would be a double-edged sword in its backyard in Ukraine as in Syria, which has become an arena for Moscow's regional and international resurgence and also in the context of the relationship with the U.S."
www.huffingtonpost.com/raghida-dergham/the-crises-in-ukraine-and_b_4876488.html