"a part of sovereign country is being aggressively annexed by their neighbor"...sounds like you are getting your media fix from Fox News
I'm not saying one side is right and the other is wrong. I'm just highlighting the fact that's it's not as simple as you make it out to be.
Russia has a lot of control over Ukraine however since over half of their exports go to Russia (and those exports are generally of poor quality that likely couldn't be exported elsewhere) and they're also heavily reliant on Russia for natural gas...