Putin wants to stay alive and in power. This requires money. Russia gets money from oil and gas. If Ukraine ever jeopardizes Russia's ability to sell gas to Europe it will be invaded and conquered within 48 hours, for example.
In Russia people are talking about how Putin's goal is to keep the Gulf States from controlling the region in hopes of getting higher oil prices by instability resulting from a stronger Iran and a weaker Saudi Arabia. Whether or not it works remains to be seen, but Russia is clearly interested in the region either way due to the fact that it is another oil and gas region.
Obviously, as the world gets away from hydrocarbons Russia will be screwed if it doesn't change things, but Putin is looking more at the short term here.
ἡ δὲ κἀκ τριῶν τρυπημάτων ἐργαζομένη ἐνεκάλει τῇ φύσει, δυσφορουμένη, ὅτι δὴ μὴ καὶ τοὺς τιτθοὺς αὐτῇ εὐρύτερον ἢ νῦν εἰσι τρυπώη, ὅπως καὶ ἄλλην ἐνταῦθα μίξιν ἐπιτεχνᾶσθαι δυνατὴ εἴη. – Procopius
Ummaka qinnassa nīk!
*MySmiley*
