There is brief statement by in the coming s and goings. Kelly just says it was not her choice. IMO it was time for Sonny to move on again. I don't why know they could not just send him off to be Brenda for a while and keep Connie on the show.
Obviously tptb want Sonny with Olivia, so that makes Konnie useless in their minds. I find this utterly APPALLING considering how talented KS is. There are so many possibilities for her outside of Sonny (which is where I'd rather see her anyway), but instead she gets tossed out like so many of Sonny's exes before her. SAD.