Of course, if you consider this town in isolation, then the above arguments in favor of Inferno hold some merit, but it's worth comparing it to other castles...
Building Devils is quite expensive. And at the beginning of the game, Gogs are weak (and there are few of them), Imps play the role of cannon fodder against faster units. As a result, it's very difficult, if not impossible, on the hardest difficulty level to quickly build everything, hire units, and capture mines. Moreover, all heroes have some useless skills, so you have to choose the lesser of two evils.
And in general, I think that the weakness of the Satanic castle is not accidental...