Why Did Downey Make 'Dolittle'?

Why did Robert Downey Jr make the critical flop 'Dolittle'?
The film is a critical and commercial flop.
According to the Atlanta Business Chronicle the film is one of the biggest disasters of the decade.
So, fans of the actor have to wonder why he chose this film after years as Tony Stark in the 'Avengers' series.
Downey is set to star in several movies, including a follow up to Sherlock Holmes.
So, why did he chose 'Dolittle'?
...The world may never know...