1)You read a manga initially it
2) You like it
3) You want to share your thoughts on it with like minded people, you join a forum
4) You make friends (virtual/real), spend time on the forum and get attached to it
5) The manga including the lead characters start turning shit
6) You won't leave, you would criticize. You are anchored to the forum now (refer point 4). Thus, you keep on reading and criticizing
If people had other people to share there thoughts with on this stuff (physically present with them), or were preoccupied with some other stuff, they won't be here. People just bond over internet and feel it is like a pseudo home. However, sooner or later, people start leaving, and before long, everyone does, marking the end of an era.