A comprehensive anti-ISIS battle plan involves fighting ISIS and Iran. Russia needs to dump Iran and so does the US.
“...Russia needs to dump Iran ...”
You might wonder why Russia is selling weapons to a country that finances the Jihad inside of Russia’s borders. Unlike the United States, which, (except under Hillary Clinton) has a department for coordinating policy towards countries with companies, any company in Russia can pay a bribe to Putin’s regime and sell anything they want. The few people who benefit, Russian oligarchs, believe they are immune to any bad results. They probably own houses all over the world and can go anywhere to enjoy the money they made. It’s the Russian people who will have to put up with the radioactive waste and constant terror raids on their children’s schools.