This is why Russia is called "expansionist". Because it likes to expand its territory.
Before Boris arrived to scupper it.
That's not what happened. I know you read some snippet somewhere that made it sound like that's what happened. But simply put, you're being played. And that's not actually what happened.
Watch the interview if you don't like the source.
Ukrainian negotiator David Arahamiya: https://europeanconservative.com/articles/news/official-john...
Video here: https://www.youtube.com/watch?v=6lt4E0DiJts
More than snippets
And lo and behold, the fact of two guys stating a certain narrative about those events (then embellished up a bit by the publications quoting them) does not make it so. Even the article you're citing about Arahamiya's version of events isn't so clear-cut about the matter (it says Boris's advice was but one factor among many) as you're making it out to be.
Perhaps it would be a good idea to switch to sites that don't have "conservative" in their URL.