Payero didn't settle in the U.K. he was homesick, had family issues and for the sake of his own mental well-being wanted to return to Argentina, he felt very isolated when he was injured and the club were hoping he'd be open to a loan move to a Spanish club for a season with the long term aim of reintegration back into the squad as they'd invested a lot of effort in getting him to the club but he really wanted to go back to South America.
In this instance it's a shame but they've done right by the player, I know it's easy to criticise but unhappy players are of no benefit to the club and it's unlikely that given his situation he'd be producing anything like his best form.