I can see why he's left, what with Red Bull forming the team around Verstappen. I'm sure he would have jumped into a Mercedes or a Ferrari in a heart-beat, but obviously they are keeping a safe set of teammates (well, we'll see about Ferrari at Monza I'm sure, but it looks like Raikkonen is now favourite to stay).
Good move? Probably not in the short-term, but hopefully Renault will start moving forward at some point, but I'm disappointed they have closed the gap to the front this season.
It gets him out of Red Bull, and if there's a shake-up at Mercedes when Hamilton eventually retires, then Ricciardo will be one of those touted to replace him (if Mercedes are still around - I'm not convinced they're in it for the long term).