It seems to me entropy has hit black metal, as it hit hardcore before it, for the same reason: a human reason, namely that everyone wanted to participate and now that they have, they have drowned out any consistency except mediocrity in the genre.
I hear constantly: "This band rules","Wow!!!!1!", "The best black metal," etc and the bands change every week and then disappear. Who remembers Conqueror? Crebain? (Lja?) Drudkh? Craft? It's all the same shit: musically OK in competence, but without soul or meaning.
What took out death metal was nu-metal because by hybridizing death metal with bouncy funk-rock, they made something even a houseplant could listen to. What took out black metal was the egalitarian spirit of the underground and letting everyone play. Now everyone has their own CD-R, label, zine, etc. and there is no one left to promote the excellent.
('cept us outsiders)