> Putin wanted this war
Yes.
> proactively
No. He could have done this any time he wanted over the last 8 years. So why now? I don't know what, but some thing has changed in the strategic calculus after the Trump administration went out. That is when he wrote about the historical unity of the Rus peoples. And everything else follows from there.
> there is only reaction from the other side.
They lit the fuse with the eastward expansion of NATO and the attempts to place ABMs close to Russia back in the 2000s. It is not as if Russia invaded some country in Africa or South America. It has invaded a neighbor, a former Soviet state for reasons of national security.