Russia-Ukraine conflict oversimplified:
Stage set by: US
Direct action initiated by: Russia
Pawn: Ukraine gov
Suffering: People of Ukrain (and rest of the world)
Target: Oil market, war machinery sales, money, money, money
Russia could hardly be expected to sit around when a hosile military alliance threatened to come to its doorstep.
Putin repeatedly warned against it. Especially since his 2007 Munich speech.