The coup happened first in Feb 2014. Crimea succeeded and was annexed in March 2014. Crimea in 2014 was 68% ethnic Russians, with only 16% Ukrainian language speakers.

https://en.wikipedia.org/wiki/Demographics_of_Crimea#Ethnicities_and_languages

Crimean leadership attempted to create an independent republic, but Crimea instead became an autonomous region in Ukraine in 1992. Ukraine abolished the constitution of Crimea in 1995 and allowed the Ukrainian central government to veto the Crimean parliament's chosen prime minister.

https://en.prolewiki.org/wiki/Crimea

So the far right uprising and coup is where this started. Then the occupation and civil war on Donbas started shortly after this in April 2014. The majority ethnic Russian oblasts did not wish to be persecuted by the western Ukrainian banderites.

https://en.wikipedia.org/wiki/War_in_Donbas