Paige was announced as the new Smackdown General Manager and the news was a surprise to everyone backstage. On Monday night when she gave her retirement speech, Paige was under the impression that she was done with wrestling. She likely would have made appearances at independent shows and conventions because she has name value but WWE had a better offer for her.
It turns out that the decision to give her the General Manager job was not made until late Monday night or early Tuesday and she was not told anything until Tuesday, just before she would have flown back home from New Orleans. This should serve as further proof of how things change at a moments notice in WWE and sometimes it just depends on Vince McMahon's mood.
The feeling on Paige is that she is well liked backstage and they wanted to find something for her to do. When she returned to action late last year, people that know her felt that it was better for her to be on the road with her wrestling friends because she would stay out of trouble. Putting her on Smackdown is a nice gesture and it shows how much she means to the company and management.
Furthermore, it makes sense to keep her around because she is part of the upcoming season of Total Divas. The E! Network filmed content during WrestleMania weekend. They also filmed her retirement speech and likely, her debut as Smackdown General Manager.