Do elaborate on what it is you're confused by. Russian strategy has been destruction of Ukrainian army through attrition. Being a much bigger country with a big industrial base, this is the most sensible strategy for Russia.

Russia spent around 9 months making sophisticated layered defences over the past year while massively expanding the army. Ukraine was then forced to use human wave tactics to attack these defences by their western partners to try and show visible territory gains for continued support. This offensive failed miserably resulting in the loss of large portions of the equipment the west managed to cobble together, as well as trained and experienced soldiers. Russia actually ended up gaining more ground during this offensive than Ukraine did.

Now, Ukraine is out of weapons and manpower, and Russia is starting an offensive of their own having recruited over 300k new troops who have been trained and equipped during this time.

On the other hand, western powers are now admitting that they're not able to keep up with the rate of use ammunition, and Ukraine is now actively drafting women in to the military. Furthermore, many western economies are going into a recession, while Russian economy is showing growth and increase in military production.

On top of all that, we're now seeing the war in Palestine unfold which necessarily means that Ukraine will get even less support from the west.

Seems to me that this is precisely what U.S. Lt. Col. Alex Vershinin predicted would happen in his article that's linked above.