The Uke persecution of ethnic Russians in the now Russian oblasts, along with the lunacy of potential Uke membership in NATO, is why the Russians were forced to act. Yes, there is a civil war aspect to this. The US never missed an election during WWII when we were actually attacked.
In 2010 Yanukovych, a pro-Russian President was elected. He did not favor closer cooperation with NATO and the EU. The US/EU engineered a coup/revolution in 2014 that removed Yanukovych. This spawned the separatist movement in the Donbas and the current ongoing war. In 2014 Russia invaded unopposed and this led to annexation of Crimea.
It is worth noting that separatist movement is closely correlated to the Russian speaking areas of Ukraine and to the election of Yanukovych. Ukrainian nationalists wanted to eliminate Russian as one of the official languages of Ukraine.