Well, the Russian frontline’s support areas have been overrun and their supplies taken. Usually that’s a sign of retreat or surrender. When their food runs out they will move while they still have the fuel to do so. But where will they go w/o orders and facing desertion charges? Well, Wagner has food, fuel and won’t shoot them for desertion....
The Ukes have merely punched through the weak front line which serves more as a recon force. Behind that are the real hardened Russian defenses. The Ukes haven’t been able to punch through that.