Indeed. You seemed to be crying out for a more nuanced explanation, so I gave it a go based on what I know.

Of course, if you have the time do make sure to research on your own. The Wikipedia page on the Russian Invasion of Ukraine actually isn't too bad if you're looking for the history so far. Other sources that offer speculation about why things happen vary in quality, but I can recommend the reporting by The Telegraph, including their Defence in Depth YouTube series and their podcast.