He was let go because the Kings wanted to be "nice" and let him sign on with another team. I think the Kings should have let him rot on the bench since he was the one that picked up his option in the offseason.
My guess is: neither. There really aren't a lot of players available as FAs at this time of year, and Potapenko was never someone we wanted to play, his only purpose was to get us out from under Skinner's contract, and possibly as an ender to trade. There's nothing left for him now but to wait out the year on the bench, or to be waived.