Sorry for being very late on this, but Mikhail Mizintsev was Deputy Minister of Defense in command of logistics in the timeframe where Wagner head Yevgeny Prigozhin kept talking about Wagner PMC having a "lack of ammunition." Since it was Mizintsev's responsibility to handle these issues, you can make a connection that Mizintsev is withholding ammunition to give to the Wagnerites because Prigozhin won't shut up about it, and hence, the Russian MoD sacked Mizintsev.
Here is where things get really weird. For such an opponent of Wagner, Mizintsev still got hired by Wagner Group PMC to be one of their commanders in the military company. Wagner PMC units also gave Mizintsev a tour around Bakhmut after they fully captured it. Maybe it wasn't Mizintsev's fault that the MoD withdrew ammunition and rather the fault of Minister of Defense Shoigu, but they needed a scapegoat and Mizintsev was thus let go, and hence to rub it on the MoD and Shoigu's faces, Prigozhin hired Mizintsev.