Well, they elected Viktor Yushchenko and "someone" accidentally tried to poison him with dioxin and almost succeeded. Then somehow Viktor Yanukovych was elected

Well, they elected Viktor Yushchenko and "someone" accidentally tried to poison him with dioxin and almost succeeded. Then somehow Viktor Yanukovych was elected, signed extremely pro-Russian legislation (after being advised by Paul Manafort, currently indicted by Mueller for his actions related to the 2016 US presidential election). Russia would probably point to NATO encroachment in areas it considered inviolate, but honestly, they invaded free and independent neighbors and annexed them... and perhaps a bit of circumspection in that respect would have been wise.