I can't see what could have prompted the move...
Even before I the player leaks came out, I would have given odds that Tua didn't beat Fitz out in practice. Couple that with the hiring of Gailey, the play of Fitz from the end of last season to the beginning of this season, and the familiarity of Gailey and Fitz and it was a mystery to me why Tua was in the lineup as a starter.
The Chamber Files. Much Ado About Tua.