It is known that Vishal Bhardwaj is a big fan of Shakespeare. So clearly he must have wanted to turn them into movies and it seems he planned to make them a trilogy at least after the second film:
"It will come because I have to complete my trilogy on Shakespeare but not in the near future," Bhardwaj said adding that he is yet to decide upon a specific play.
But he had to be sure, and when his first one was well accepted by people he must have gone to make others.
My theory is based on this article from 2009.
And here are some more proofs:
“My engagement with Shakespeare happened accidentally. In school, Shakespeare horrified me. Ninety per cent of directors want to make a gangster film, I was keen to go beyond the surface, say more than just killing,” Bhardwaj told an audience in Asia House this week.
Another article that suggests his love for The Bard