Morbyd
Moderator
That's the story I heard as well.I might be wrong but I think they were instructed to do this by officials to avoid a change of mood and outbreak of panic in the crowd.
Many people were unaware it was all going on and I guess it was important for crowd control to keep it that way.
One of the artists interviewed on BBC was quite distressed that he had to play on knowing that people had died. Nevertheless, it might have saved lives.