Why was Aishwarya Rai replaced in the movie Chalte Chalte?

Salman Khan and Aishwarya Rai's love story had all the elements of a typical Bollywood film- love, heartbreak, sadness, anger, and finally regret! The duo began dating while they were shooting for Sanjay Leela Bhansali's Hum Dil De Chuke Sanam. However, the love soon turned into an obsession. Ash felt that their relationship had reached a dead end and chose to give up on Salman in March 2002. It all started when Aishwarya's ex-boyfriend Salman Khan drunkenly created a ruckus on the sets of Shah Rukh's production, Chalte Chalte. SRK did not take it very kindly and replaced Aishwarya with Rani Mukerji. What do you guys think about this?