I feel like Kemosabe/RCA (Sony probably were involved too) just saw how the song was well received so they thought it was a perfect opportunity to make money, as well as showing the GP that they have allowed Kesha to 'record' with other producers. After this song, no doubt they won't allow her to release and be sketchy, it was probably a one off thing so they could use it as an excuse that shes 'free'.