No, you are right, it was Wagner attacking. But they were well supplied regardless of what Prigo said. And yes, he was using his own conscripts (the ones he got from prison and didn't have to pay) as as cannon fodder as well. They lost 30% of their force in Bakhmut because Prigo wanted to show a victory in order to make an argument against disbanding the PMC and absorbing it into the regular Russian military and thereby depriving him of a very lucrative contract.

His unhinged rantings against Shoigu and Gerasimov were basically because they disagreed with what Prigo was doing.

Still, it was Zelensky's obsession with holding Bakhmut that was so disastrous for the AFU. They lost 2x as many men as the PMC.

When it comes to annihilating cannon fodder, it helps if you have a 10/1 advantage in cannons, which is what Wagner had, courtesy of the Russian army.