WWE decided to keep him on TV doing the same routine he'd been doing for two years. Then they randomly swerve turned him last night at their TLC pay-per-view.
That 'The Essence of Excellence' became a good guy by saving the Spanish announce team from the Three Man Band says a lot. Mainly that the turn, as well as Del Rio himself, were an afterthought for the show.
The smile of a babyface
Performers should switch from good to bad and vice versa based on reactions from the crowd. Very occasionally there's call to turn someone based on how long they've been in a particular role. The Miz was recently switched for a combination of both reasons. He'd been a heel for most his six year stay on the roster and fans were eager to cheer him. That was a switch that made sense.
ADR was not in the same position. Fans were not yearning to cheer him and there were plenty of people he could have been pitted against without altering his character. He just needed a break for a while to break up the monotony.
Handled right I'm sure Del Rio can be valuable in his new role. He played a tecnico (Mexican babyface) for much of his pre-WWE career and was said to be reluctant to go bad when first signing with WWE.
His biggest task is likely to be winning over WWE's fans. They've been conditioned to boo him since he first showed up. Xenophobic aristocrats are not natural good guys. Nor are people with their own personal ring announcers. ADR's going to have his work cut out for him in his new role. There's only so much character tweaking that can be done.