First, Russia didn't just recently become involved in Syria. The then Soviet Navy built its facility in Tartus, Syria in 1971. The Soviets, and now Russians, have maintained a continuous presence ever since using it as a maintenance facility for Russian navy vessels operating in the Mediterranean.
Second, the CNN articles (along with the rest on Western media outlets) has Mr. Kerry taking a strong stance against Russia and tries to make it look like more Russian aggression similar to that in Crimea. I am always leery of Russian actions that may lead to conflict with the US but in this case, CNN and others are showing their biases.
Russia has had a long relationship with Syria and the Syrian Ba'athist Party (of which Bashar al-Assad is General Secretary as well as President of Syria). The US has long opposed the Ba'athist Party and al-Assad which is why then Secretary of State Clinton and Mr. Obama supported the Arab Spring back in 2011. Clinton and Obama wanted to see al-Assad go the way of Qaddafi and Mubarak.
Perhaps you remember the now infamous "red line" Mr. Obama used to warn al-Assad against using chemical weapons against the opposition? Most people, myself included at times, point to this as just one of many examples of Mr. Obama's unwillingness to follow-through. The real reason though may have simply been Russia had sent several warships and Russian Marines to Tartus. Had a US strike go awry, it could have escalated things between Russia and the US at a time when the Obama Administration was still pretending relations were copacetic.
The Arab Spring did not oust al-Assad, if anything it made his hold on power stronger. It also increased Russian support of his government. Now comes the little embarrassing part for the US and she-who-would-be President; the opposition group that the US supported (and which Russia opposed) became, what for it, ISIS!
CNN and the other Western media outlets do a good job of only relating stories from a pro-Obama standpoint. Russia's increased presence in the region is to support al-Assad….which means they are there to strike ISIS. So what's the problem?