It was predicted that after initial setbacks, Russia would gear up production and eventually overwhelm Ukraine by sheer volume of weapons and number of troops.
I suspect Putin thought Ukraine would fall quickly, as Poland did to Nazi Germany in 1939. Now it's dragged on for over a year and a half.
Instead, it's looking more like a repeat of 1941/42. However, the wild card here is that during WWII, the West supplied the USSR with weapons. This time the West is supplying Ukraine.
In other words, I have no idea how it will turn out. It may go indefinitely. Both Putin and Zelensky need a face-saving way out, in which both sides declare victory.
This could be the culturally Russian parts of Ukraine being ceded to Russia, and Russia paying huge reparations to Ukraine.