All of you are so wrong!
The real reason is this:
Satoshi Nakamoto FARTED and MOVED his coins!!!
joke aside, it could certainly be that satoshi is playing with the market and his 1M coins, whit that amount he can manipulate any exchange like nothing, he can even manipulate multiple exchange without problem
Come on I thought Satoshis addresses are well known and monitored all of the time! If he would move one his coin the whole Bitcoin world would know this in the next 5 minutes!
I highly doubt this is possible!
not all of his coins are well known, he was mining even when other joined(and you was still able to mine a big portion each day, for example one person that i know was mining 1k btc every 3 days in the summer of 2010), so a big fortune is still unknown, he only need 100k to move the market