It appears that mathematics of attrition are beginning to function in Russia’s favor. Ukraine may have simply not had the troops to defend the area.
They average Ukranian Soldier has been screwed by the military and political leadership of the country, they have stolen the money intended to support the soldier.
Sooner or later the mathematics of attrition and realization of the soldier that this battle is pointless will set in, we may have reached that point, and the Russians will overwhelm them.