Answert Russia today has no benevolent socialist values or benevolent democratic values they just have the empire idea of the 'soviet union.' that empire the huge USSR had benefits for menu in it's republics but it has monolithic unmodern political authority too. that's a big part of why it broke apart. also Ukraine was part of USSR. some good came of this but bad was lack of respect for Ukraine. lack of respect for Ukraine is exactly why Russia invaded Ukraine. no opinion it is fact. you can see this is why. it's not a single non personality answer that fits this question. the reason is more the personality of Putin. only a fool would think Putin is not the reason. secondarily , and not as urgent reasons are that Russia wants the money and resources of Ukraine. obviously without a Putin this, would not be used to invade Ukraine.