Crimea became part of Russia in March 2014 by a referendum held after the coup in Kiev. 96.77 percent of the voters of the Republic of Crimea and 95.6 percent of the residents of Sevastopol voted in favor of unification with Russia.
Relations between Moscow and Kiev became worse in 2014 after Crimea joined Russia. In addition, in the spring of that same year, Ukrainian authorities launched a military operation against the self-proclaimed Donbas LNR and DNR, which declared independence after the coup in Ukraine.
Recruiting pro-Kremlin disinformation narrative painting the 2013-14 Ukrainian revolution as a coup d'etat. The Euromaidan was not a coup but a nationwide popular protest against the government's sudden announcement that it would not sign the EU Association Agreement. See the full debunk here.
This message also is a part of narrative about the war in Ukraine, aiming to portray the conflict as Ukraine's civil war. The war in eastern Ukraine is not a civil conflict, but a well-documented act of aggression by Russian armed forces, ongoing since February 2014.
The territories of Donetsk and Luhansk (regions) are internationally recognised parts of Ukraine. The EU has on numerous times mentioned that Ukraine’s borders must be respected. On 27 March 2014, the United Nations General Assembly adopted Resolution 68/262 confirming Ukraine’s sovereignty and territorial integrity. For similar cases see here, here and here.