A lot of people in Eastern Ukraine identify themselves as Russian (source: a friend of mine near Poltava). They speak Russian first, Ukrainian second. Trying to argue which came first is rather moot, the tug-of-war between eradication and strengthening of the Ukrainian identity has been going on for more than a century (see [1] and [2]). There's nothing obvious about that cultural conflict, except perhaps to Putin, who is clearly more interested in Rusifikatsiya than in Korenizatsiya.

[1] https://en.wikipedia.org/wiki/Ukrainisation

[2] https://en.wikipedia.org/wiki/Russification