Just another theory which might be part of the puzzle..
1) Both the REAL BTC and USD were long ago channeled out of MtGox, MtGox operating a fractional reserve (somewhere between june 2013 when Karpeles proved he had 424k BTC under his control and now
2) He kept just enough funds in the hot wallet to be able to pay out withdrawals with whatever more he made out of fees
3) Intentionally he delayed withdrawals, leading to the USD price on gox shooting up, allowing him to do arbitrage with the complicity of another exchange and people close to him, traveling to receive the USD directly in japan and channel it back to the exchange conspiring
3.b) There was also probably a bot running on MtGox profiting from the smallest difference in buy/sell, being able to trade at no fees.
Another way of manipulation used, was to deliberate shoot the price up and down in sharp spikes, sending signals to other exchanges, and being able to buy/sell with pre-knowledge of where the price would go.
Since the goxBTC/goxUSD were not real anyway and via manipulation he had a large piece of them, it was easy for him to control where the price goes.
4) At some point when there was not much to be made anymore with this scheme, as people would simply not deposit USD anymore into MtGox he decided to pull the plug of BTC deposits as well
5) The intention to pull the plug on BTC deposits was to create a panic and shoot the BTC price down on MtGox. This allowed him to buy up a lot of cheap goxBTC along with what he already had on the exchange.
Those goxBTC and goxUSD were already worthless as not backed up by REAL btc/usd. They were just IOUs
6) Knowing the goxBTC he holds is worthless, he dumped them all in one go, creating another mass panic and shooting the price down to 91.5 USD, allowing him to buy even more BTC at the bottom, followed by a sharp spike up, creating another panic.
Rinse and repeat until he has shaken out the very last bit of most customers both in goxUSD and goxBTC.
7) The final kill blow was when he again used the now massive amounts of goxBTC to shoot the price down to 135 and close shop
Now that shop was closed, he could file bankruptcy and claim he owes people only 135 per BTC as this was what they were trading for at this point before shutting it down. Not allowing others to channel money in and buy the price up again
9) With all the manipulation he managed to drive down the liabilities to his customers down to a minimum
10) People thinking they lost all, in shock, will be grateful to even get 135 per BTC once this is over. They will be willing to sign anything anything to get at least something out, preventing them from further demands in the future
11) Gox will rise up again under a new label Gox.com, now having millions of scammed BTC and USD in their pockets, while having had to pay only 1/10th of liabilities to the former customers