What up with the massive dump ?
But still i dont understand where that 35k coins come first to Polo..?
Those 35K coins, were the XCP deposits in Poloniex central account. The white hat hacker, withdrew these coins from the central address and deposited it back to Poloniex and sold then on the exchange for a low price.
The order depth in Poloniex was around 100 BTC. So, the hacker took these BTC, but left some of them in the exchange.