Eh? Although we don't know the details, if a key reason for him going is Rodgers, and the vision Rodgers has sold him, then if I was in Sigurdsson's boots I'd be fairly pissed off if the person who has persuaded you to come to the club permanently (could include relocating, moving family / away from friends, and the other things associated with moving clubs like this) has decided to fuck off.
Sigurdsson's well within the realms of decency to change his mind here.