Yes, good targets.
Muzzle loaders are capable of great accuracy. But the traditional styles are really an antique firearms system. That is the charm to those of us who shoot them.
As for the 790 yard shot. I feel certain that was not a traditional style ml rifle that was used. And, yes, the hit was simply lucky. The trajectory had to be, literally, rainbow like. The bullet was falling at that range. It was not a shot 'at' the animal but a shot in the air they hoped would come back down where they wanted it. A very unsportmanlike shot attempt, IMHO.