hmmm
dont think the music thing was a big threat
whenever a TV serial, song, game or ebook bundle is uploaded on a file sharing site, there are many people who share these links on say twitter or even facebook. Now there is someone paid to protect all this intellectual property, and they send cease and desist notices and report each and every one of these users, or at least, many of these users, for a site like twitter, they have to necessarily ban the account, and remove the tweets that link to the infringing content
in short megaupload was actively encouraging piracy with its very existence, so they made many, many others commit the offense
think this played at least a partial role in the kind of action taken against them