What caused 5,000 trapped Russian soldiers to retreat this week | Russian Victory Day defeat

Is this the start of something big in the Ukraine war as the Kharkiv section of the Russian invasion begins to collapse. Something has changed and the Russians are running away from Kharkiv trying to avoid being trapped and captured. In one week the Russian line has started to collapse to the point where desperate Russians are destroying bridges as they retreat at high speed. How did it happen and could this be the start of a Russian military collapse in Ukraine?