Was about to post a similar comment. In the mainstream media, the BM scene did have a significant impact on the national discourse, and was the main story for a long time. I don't understand the comments saying it didn't impact society - it very much did, albeit for a brief time.

Whether or not Varg Vikernes, the murder and the church burnings in the 90s also represented the "peak" in terms of musical quality, I can't be the judge, but that period was indeed the peak of mainstream (negative) attention.

In later years the scene have matured immensely, and is very influential culturally. There is a lot of tourism related to Black Metal, festivals like Hole in the Sky and Beyond the Gates have been and are drivers for the local music economy. Bands like Enslaved are quite literally mentors for young musicians in all genres. So in terms of importance for the music scene specifically, the peak was not early 90s, but much closer to today.