ok, theory.
Putin was Allies with Syria and Iran only to have a fighting chance of staving off the deep state from regime change in Russia. Now that the deep state is weak and vulnerable Putin decides to joun Trump against the deep state and in doing so he's taking a huge risk and putting major faith in POTUS to team up and defeat them for good. So Putin will throw Syria and Iran under the proverbial bus to join US and deliver the kill shot.
IMO