The Donbass region is largely ethnically Russian, and has been systematically oppressed by Kiev, including erasure of the Russian language, and outright massacres following the secession of Donetsk and Luhansk post-Euromaidan.
Additionally, the USSR never colonized Ukraine, neither did the Russian Federation. The Banderites that took over Ukraine in 2014 are far-right nationalists, and as such are useful for NATO.