There are a number of reasons.
Russian pipelines run through Ukraine. Ukraine charges Russia billions in fees for the privledge.
Nord Stream 2 pipeline is coming online shortly. Sanctions didn’t stop the building of the pipeline.
Ukraine gained independence from Russia on agreement to give up its nuclear capabilities
Russian businesses and Ukraine maintain the second largest migration border in the world. The first is our southern border.
Foothold on the Black Sea. This give Russia a larger military presence on the Mediterranean, Middle East, and North Africa
Further economically Putin wants a Eurasian Economic Union. Do that treaty, while signed, has been failing to come to fruition.
For Putin, this isn’t about restoring the Soviet Union. It is about becoming a major superpower in a now very unstable world.
And, what's wrong with that? He is looking out for the best interests of his nation. That is what he should be doing.
It shouldn't be any of our business so long as Putin isn't threatening to invade countries and take them over against their will, which, unlikely China, he is absolutely not doing.
All this focus on Russia is happening while we do virtually nothing about the real threat - China. China is doing what we falsely claiming Putin and Russia want to do. China enslaved the people of Hong Kong. It has threaten Taiwan. It's buying up land in this country and in other countries in the hopes of gaining economic dominance.
If anything, we should be seeking to work with the Russians to keep China in check.
There are reasons, however, the far left and globalists hate Russian. Obama, Biden and Soros have for years sought to demonize and destroy Russia. He's threat somehow to their agenda.