Conversation so far:
What is The New 52?
The New 52 was the 2011 revamp and relaunch by DC Comics of its entire line of ongoing monthly superhero comic books.
Where is The New 52 set?
What is the Riddler up to in The New 52?
Riddler appears as an inmate at Arkham Asylum in Batman #1.
Is the Riddler in the Arkham Asylum in The New 52?
Riddler appears as an inmate at Arkham Asylum in Batman #1.
Is the Joker in Arkham Asylum in The New 52?
The Joker secretly hijacks Arkham Asylum.

Question: Why did Joker hijack it?
Self-contained rewrite: Why did the Joker hijack Arkham Asylum in the New 52?