From what I understand, Prigozhin advanced Wagner into Bakhmut beyond what the Russian MOD was willing to support, leaving the flanks vulnerable. Wagner kept advancing, Prigozhin kept begging for support, the Russian MOD ignored him as much as they could. Now there is a opportunity for Ukraine to hit the flanks around Wagner and retake Bakhmut.
This is what happen when your army is actually several armies, each having different political objectives, the leaders are no better than feudal lords with their own ambitions, instead of officers in a unified command.
Good analysis.