Well celebrities are high-profile targets and so much of their information is public knowledge due to the massive amount of interviews they do (plus all the daily tweeting and instagramming of their personal life).
This innocent tweet from actress Julie Benz probably revealed the answer to one of her security questions (pets name) for example. Most security questions/answers for celebs could be found in a two second Google search - we know when and where they were born, their mothers name, pets name, basically everything.
The only way to make these typical security question/answers secure is by putting in random gibberish and storing that in a password manager. When a website asks me what is my mothers maiden name or whatever, I put in something like "eFsDGxW4TcjK=Mfj.u8cRT" which is randomly generated, impossible to guess, extremely difficult to brute force. Not everyone uses password managers though and they end up picking something easy to remember which is also usually easy for others to guess/research.
I do think Apple (and every other company) should send out an email with some basic security tips. Raise awareness of things like two-factor authentication and maybe even provide some incentives for people to secure their account with 2FA, like a free iTunes song credit or an extra gig of iCloud storage or something.