On Reddit some seem to believe that it was an AT round (pure kinetic) and not HEAT, and that the round was aimed at the engine. Hence no detonation and why the mounts were able to survive without disabling injuries. Also the fact it was an IFV means its armor was thinner than a tank and the round was a through-and-through without bouncing around inside, causing less damage than it would if it was more heavily armored, like a tank.