Why attack Mumbai though?
In addition to any idiosyncratic and perennially malleable claims made by the gunmen ("Deccan Mujahideen"), Mumbai is the economic centre of India, its New York, which is a strong lure; perhaps it is to stymie ongoing peace negotiations (Re: Kashmir) with neighbouring Islamic state Pakistan; and maybe also to destabilise India as a cohesive modern democratic state by inciting internal rifts.
The persistently luminous Barrack Obama released these comments...,
The United States must continue to strengthen our partnerships with India and nations around the world to root out and destroy terrorist networks. We stand with the people of India, whose democracy will prove far more resilient than the hateful ideology that led to these attacks.”
Coincidentally, this Sunday morning National Radio's Chris Laidlaw hosts a feature on Pakistan and its fractured ominous situation.