There was a time when Russia invading Ukraine was a strategic economic move, but that doesn't really make sense to me at a time when the world was focused on China and the EU was ready to buy Russian oil in large quantities. On the surface level, the timing of this feels really backwards. Many conservative talking heads speak of this as though Putin is trying to take advantage of a weak moment for the US, but even setting aside the bias on the US part of that analysis, Russia just doesn't have the capability to actually occupy Ukraine, even if the won the war.
Putin says it's about Ukraine joining NATO, and I think that might really be the issue. I'm beginning to think Putin isn't trying to recreate the USSR, but rather is trying to create his own North Korea, where he can isolate his people through saber rattling, negotiate a demilitarized zone in the west, and then lean on China to bankroll his dictatorship. The ties between Russia and Ukraine threaten that, especially if Ukraine joins NATO, so he needs to forge a geographic barrier on that border.