>>283236390
It's not a coincidence that the most successful horror anime have been OVAs or movies.
The point on runtime is false though. Tales From The Crypt was a very popular anthology show that ran for 7 seasons, and that was 30 minutes per episode. For an actual /a/ example, there's the Devilman Lady anime that went all in on the horror aspect of the Devilman mythos in TV format.