He yearns for the old days, with him in charge.
Putin wants Ukraine. For a long time now. So far, he has been taking a bite whenever he thinks he can get away with it.
Remember when all mention of Ukraine was taken out of the COP platform during the 2016 convention, probably by Manifort? Under Trumps orders. Who might have been following orders himself? Or how Trump wanted to slash troops in Germany, cut NATO's budget?
Had Trump won 2020, the invasion would already be underway. Now, Putin is hoping for the chaos in the west (that he has helped create) to distract us from his plan.