Because it's becoming increasingly hard to explain this hack otherwise.
Imagine you walk by the beach, and see that the sea has washed up a pirate treasure chest. You crack it open, and see it full of gold, jewelry, old manuscripts, letters. Would you just throw the chest back into the sea, taking only a single ring, and a nail from the chest to hang a price list on your lemonade stand with?
Because that's what happened here. The attackers hit gold, and threw it all away.
After reading Krebs' initial take on the incident[0], I think a plausible explanation is that whoever created the hack isn't the person who exploited the hack.
The hacker managed to get an amazing level of access, but exploiting that, and extracting value from it, and getting away clean is probably really hard. So they sold the access to whoever was willing to pay for it for a guaranteed return. That also gives you an extra middleman that law enforcement has to get past before they get to you, and confusing the trail between the middleman and you might be easier than confusing the trail between your targets and you.
Except whoever paid for the access and used the exploit just didn't have the imagination to do something that made as full use of the hack as they might have done. And now dozens of other criminals are facepalming themselves to death for not having been the ones to have bought this opportunity for their own ends, which they think would have been much more epic.
What "real treasure"? It's hard to beat the opportunity to do large-scale stock market manipulation, play some ninja geopolitics, or even download private messages of rich and influential VIPs. And that's the opportunity the attackers didn't take.
Imagine you walk by the beach, and see that the sea has washed up a pirate treasure chest. You crack it open, and see it full of gold, jewelry, old manuscripts, letters. Would you just throw the chest back into the sea, taking only a single ring, and a nail from the chest to hang a price list on your lemonade stand with?
Because that's what happened here. The attackers hit gold, and threw it all away.