Didn't he first put the wall up at $280, take it down for an hour or two, then put it back at $320? And it was getting nibbled at $320 too. Then it disappeared and came back at $300, where it was obviously got eaten until gone. I really don't understand why he moved it from $320 to $300 given that it was getting action at $320...*iff* he was (even poorly) rationally trying to price-maximize.
Obviously tossing up a single 30k wall doesn't make too much sense for someone who's primary objective was rationally selling that stash. But I can maybe buy the theory of an irrational/undisciplined/freaked-out holder *except* for the move from $320 to $300, since there was indeed stable action at $320.
The only fully rational motivation I can see is if he was trying to achieve a low but stable price for a period of hours during which to secure an OTC deal in the other direction. He tried $280, but it was unstably crashing the price, so he tried $320. He got good interest there with a stable price, so he decided to see if he could do better and keep things stable at $300. Price pegged right up against the wall without crashing, so he stuck with it, and priced a bigger buy deal on OTC based on a stable price of $300. ...
Who knows... Not all players are rational, so it could be anything. Whatever; even the big trades are insignificant noise in the long run.
What about this: he was afraid that the price would just keep falling if he waited too long, and decided he had to sell in a few hours at most. He asked 280, saw that there was enough demand, tried at 320, saw that it was going to take a long while, so moved to 300, and it worked well enough for his purposes.
He didn't have it at $320 for very long, IIRC (less than an hour?), and it was getting action the whole time. The action during the first hour at $300 seemed similar; it took a few hours to really get going. Though maybe my memory is off; I was doing other stuff while glancing at the book/wall periodically.