According to this article Rose wanted to close on the $60 million deal, but the Digg board told him he could not. They thought the company would go further but didn't take into account Rose's short attention span. A later $200 million deal with Google was withdrawn by Google.
Apparently Rose has made money from selling early shares and from smart early investments in companies like Twitter and Square.
Rose has done some very interesting interviews called "Foundation" (on youtube) which mainly focus on the interviewees. Rose doesn't really come across as an especially greedy person.
Clearly then, the blame belongs with the Board. It was a stupid miss on their part. Good job to Rose on making some savvy financial decisions. I supposed the “greedy” board motivated him.
Can you post a link to his interviews?