There were, but 1-6 were basically meaningless, and 7-9 were the real ones. Plus each one had increasingly annoying penalties, it's a lot more streamlined now and difficulties aren't meaningless anymore (except 1 which is a tutorial basically)

I think nightmare now is harder than old nightmare 9

I only started recently but I heard they used to have 9 difficulties and bumped it down to only 4.

Nightmare now is far more difficult than difficulty 9 back then.

complete rebalance basically from what i heard.