It is not as much money as pundits probably think it is worth. And also, trying to negotiate a blackmail is time consuming and opens the risk of being caught especially if it a high profile target, with no guarantee of being paid. Do you really think someone like elon musk will pay a bitcoin ransom assuming there is anything incriminating? Paying off a blackmailer is an admission of guilt and does no good if the info is released anyway.
It also depends on how sophisticated the thief was. Did he have everything automated to dump anything everything from the inboxes while automating the posting of the spam tweets, or was he frantically doing all his postings by hand before twitter could shut it down. If the thief is not sophisticated his main priority would probably be making as much money as possible with the posts and ignore the private messages