The 4chan Cycle

PHASE 1
After a long period of lenient moderation, some big drama, or another thing, a board goes to shit, flooded by shitposters, redditors, and and other undesirables.

PHASE 2
Action is taken--moot recruits a new mod, tells the current mods to do something about it, or a mod decides to take matters into his own hands.  Because moot makes terrible decisions and 4chan mods are, and always have been, terrible, this makes a lot of people angry.

PHASE 3
Stupid shitty drama.  A bunch of people declare the board (or the entire site) to be dead and leave for another board or one of the many little splinter *chans out there.  Most, however, stick around, even those who claimed they were going to leave.

PHASE 4
A short period of peace.  The mods calm down or are forcibly removed, the shitposters have moved on or been banned forever, and the board is calm and vaguely usable for a while.

PHASE 5
Over time, newfags, redditors, shitposters, etc. trickle back in.  The cycle returns to phase 1.