1. A buyer truly believes that Gox death would mean Bitcoin death or stagnation for 5-10 years and, thus, his own coins would be worthless anyway.
2. A buyer believes he can make more than 770k BTC he'd have to pay back customers.
However, I don't really think they've lost that much. It is simply insane. I don't believe anyone can be that incompetent, especially after reading Mark's 2012 message about security here: https://bitcointalk.org/index.php?topic=23938.msg1177353#msg...
Update. Rumor on twitter about the acquisition: https://twitter.com/paulbuitink/status/438428157948219392