Elphick had just got over a very bad injury, which took two operations to put right. He was 4th choice defender, so a bench warmer at best. It wasn't really known if he would develop any more because of the Achilles, & he had the chance of regular football at a division below.
Looking at Dunk's...
I know it's an Nsc mantra, but who knows if those three players would have developed their games, in the same way, had they stayed with us? Somehow I doubt it.
Edited to add, you can also blame the board for only offering one year deals to Elphick & Cook when Bournemouth offered them three...