After the fascist coup, Crimea and the Donbas very reasonably wanted to separate from the new government. The coup government reacts by sending fascists to occupy the Donbas. Russia waits for almost a decade, trying multiple times to make a deal with the coup government and its backers to leave the Donbas alone and let it have some level of autonomy. The coup government repeatedly violates both of the Minsk agreements and continues killing civilians. Russia finally accepts the request from the DPR and LPR to send troops into the region. Ukraine continues attacking the Donbas and eventually Russia and the Donbas republics decide that they have to enter Ukraine in order to stop the attacks. During this time, Russia attempts many times to negotiate a peace deal, which Ukraine's coup government almost accepts until some imperialist mascot like Boris Johnson travels to Kyiv and tells Zelensky not to accept the deal. As a result, the war continues.

but clearly this is all Russia's fault