Sorry - I still truly feel that if EVERGREY or KAMELOT (Just two examples of bands who are extremely liked in this circle) acheieved mainstream success a large majority would find a reason to no longer like these bands............
How many people no longer follow DragonForce, Opeth, etc, once they achieved greater success?
Its not like their music has gotten any worse or anything.
I think people forget that a large part of what has ALWAYS made heavy metal so great is the feeling that you are part of a smaller sub culture of music fans who are in the know of something amazing. Once a band breaks out big, something is lost.
Sure, sometimes the loss of appeal has to do in the decline of the quality of the music (IE - In Flames, etc), but heck, GHOST is already no longer discussed in most underground circuits anymore, and that took less than 12 months!
I have never been to concerned as to "why" the bands I love aren't tearing up the charts, when what is tearing up the charts or the $$$$ earned on tours is 99% crapola (To me anyways).
I also think this is what is hurting many start up festivals as well.
There is nothing wrong with being a band or festival that draws no more than 200 or 300.
As long as you are smart with your promotions and expenses, you can make it happen.
If extreme profit and prosperous living is what you are after, then playing metal is not the smart way to go.
This is the reason why MANY metal musicians do non-metal or tribute bands on the side.