First, the people you refer to as Russians are Ukrainians who self-Identify as ethnic Russians, and as of the last census (2001), they constituted only 17.3% of the Ukrainian populations and were minorities in every district in the Donbas. In Crimea, ethnic Russians comprised 58.5% if the population, but in both cases there is no reason to assume that Ukrainians who identify as ethnic Russians want to live under a Putin dictatorship.
Simplistic narrations of Ukraine’s East-West ethno-linguistic divide fail to capture the country’s cultural diversity and the complex interplay between ethnicity and language.
www.eurac.edu
en.wikipedia.org
For more discussion of Ukraine's population, google "ethnic Russian percent of Ukrainian population", and you will see the numbers I have used are widely accepted everywhere but in Putin's Russia and in the sad twisted minds of Putinheads.
None of this provides any justification for Russia to start a proxy war against Ukraine and use it to justify an invasion with Russian troops, trampling on the rights of the great majority of Ukrainians, including many who identify as ethnic Russians, and steal their land, their wealth and even their children, other than to satisfy their imperialist ambitions.
There is no rational basis for thinking NATO in any way threatens Russia's security, but it does place a huge obstacle in the way of Russia's imperialist ambitions.