About who they hired to make the coins, I don't know for certain but I just like to think it became like a low-paying job that the better artists and engravers out there wouldn't have gone for. Also I feel that the imperial governments just lost interest in making good, artistically styled coins (although I understand that the Western empire's situation was not productive towards the redevelopment of these kinds of coins). But hey at least they put a bit of effort in the solidii
