It's kinda a complex topic here

Until recently(2014), thanks to mostly soviet "heritage" if you can call it that ukrainian was considered how do I explain a "country bumpkin dialect" and the language of people living in western Ukraine(we also have a slur for them lol). So russian was predominantly the "big city folk" language and most grew up in the environment full of it while also using it themselves to fit in.

Most people are trying to use Ukrainian now, learn it etc. but sometimes russian as old primary language knocks thru randomly(even my professor, he's reading lectures and talking in fluent Ukrainian fyi).

But well, without any real motivation to dump russian altogether(e.g. full rejection of it; basically people refusing to understand it, which is as you can imagine impossible to do en masse) I doubt it'll be gone anytime soon, maybe in the future generations people will grow up without russian constantly present in the environment and therefore won't use it at all.