The idea was to get the Divas Title off of Beth Phoenix so Kharma can get the belt without facing Phoenix first. The plan as of a few days ago was for Nikki to win the title, likely at Extreme Rules, and then get destroyed by Kharma the next night on RAW. Obviously plans were moved up and the title change happened on RAW last night. Kharma destroying Nikki Bella for the Divas Title would have brought her back into the storylines as a dominant force and would have ended the Kharma-Bella storyline that began last year.
Even though Nikki won the title last night, PWInsider reports that nothing new has been said about The Bella Twins leaving WWE at the end of this month. It's still possible that they came to terms on a new deal but that's not the word going around.