I think the 7000 BTC figure is the amount of profit the site made in the past. Most of that profit would have been earned by the people bankrolling the site rather than by Dean himself.

Dean will still have made a decent amount from the site and so the question remains as to why there's any need now for an ICO rather than Dean keeping the profits from himself. I guess the answer would be that he would rather share the risk of losing with ICO token holders rather than bearing it all himself. But that's just my guess.