Political Memes

The EU-Ukraine agreement wasn't the single issue in 2014, though it the catalyst. Economic integration with the EU was seen by both the West and Russia as a vital step in reforming Ukraine so that it could become part of the Western alliance - this was said explicitly over and over in Western capitals and NATO papers. Inside Ukraine it wasn't seen that way, as most Ukrainians wanted to enjoy good relations with both sides but to elevate themselves to Western standards - until 2014. For Russia however, it meant the end of economic influence which was its chief way of exerting political influence to keep Ukraine neutral or friendly, and for an important subset of Ukrainian security and political actors who would win out during 2014, it was in fact a path to NATO.

You're forgetting that Euromaidan was first and foremost a nationalist and anti-Russian movement, and that the ethnic issue is really what led to the civil war and Russian hostility to Kiev. People for some reason tend to overlook this when talking about EU, NATO etc. The real litmus test for Russia as to whether Ukraine would become a "hostile" (ime pro-West) state was Kiev's relationship with ethnically Russian regions of Ukraine.