@fragout, it's pretty common knowledge now that the Tokyo Whale has been dumping. He had 1.9 billion dollars remaining that he could sell. Now it's estimated he has about 1.7 billion left, if he continues to try to get around $10k each. If you pull up a BTC price chart for the past week or so, you can clearly see each time he dumped.
He already sold enough to pay off creditors. The proceeds now go to MtGOX owners. 

There is a court date scheduled sometime in September. Some people speculate that he won't sell more until then, but there is no legal binding preventing him from doing so. Yes, OTC sale would be better for everyone, and they would likely fetch a better price, as bulk BTC usually costs more than market rate.
It's likely they just wanted some fast cash. / And/Or crash the price so friends could buy it up.

Here is one of many articles: https://www.ccn.com/bitcoin-drops-8300-mt-gox-trustee-sell-off-continues-market-drops/

@easyrimka, the lastest big news is the reopening of Coincheck, and the repayment for stolen XEM.