Apple and other large businesses get fined nowhere near what they have in assets.... no matter how bad their actions are. One billion is just crazy in this case...
Because Apple is not inflammatory in the court. You cannot go into a court and behave poorly, especially in the a case covering murdered children and expect a jury not to punish you to the full extent of their capabilities.
The ALAB podcast has a fun theory on the subject that while ostensibly your success in court is a matter of law and procedure, but the underlying test you've got to pass is "who's the asshole here?". Because the judge is going to decide which party is the asshole at some point, and part of the job of lawyers is to make sure it's not them and their clients.
On the other hand, Gawker network was completely obliterated for copyright infringement over the Hulk Hogan thing. That seems more disproportionate than this.