The innovation that last and sustained because public voted with their feet and accepted it. Wagner original ideas of the music drama succeeded because people voted with their feet and supported it l even if he was controversial l in his day that controversy subsided and Wagner became part of conventions for good or bad.
Yes people may argue that Beethoven and Bach weren't popular until after their death but the fact was that eventually the general public tested their innovation and accepted it and voted with their feet to support it even if it took them a while for them to process it and accepted it.
The 20th century is that the innovation can be rejected by the general public but the work can still be considered good.
Atonal music is still rejected by the public outside incidental music (the only place where atonal music is accepted by the general public is in soundtrack for films depicting dark disturbing themes which I have already acknowledge is it's only functional use) 100 years after in was invented. Yet it's still considered important innovation even though it was tested by the public and failed. No point saying Bach and Beethoven weren't popular in its day, when eventually they became popular and became part of the music furniture, but atonal music to this day will still clear the room. If it not going to be accepted 100 years post invention I don't think another 100 years will make any difference at all.
So why is atonal music is considered important, because the values of academic no longer believe that the goal of the artist is to serve the public anymore and they think they are above he public