I am 100% for decriminalization of child porn possession (just thought I would add that since everybody else wants to point out their beliefs on the subject), but just talking about the encryption, they probably cracked it because he used a shitty password. Most people are probably not using very strong passwords. Even passwords with 80 bits of entropy are not considered secure anymore, and that is equal to roughly 80 characters of English text (ignoring PBKDF stretching).