I don't see how that first tweet means he didn't want to leave the club. I read it as he did want to leave the club, but not when he was out of contract.
Murphy is one of those players (like Faddy) who says and does the right thing, and is rightly respected for that. After his European and youth international exploits, I can't imagine, however, that he doesn't harbour ambitions to test himself elsewhere.
He's still a youngster, but managed to clock up about a couple of hundred appearances in the Claret and Amber. Apart from winning a trophy, he has probably achieved about as much as he can with us and I'm sure his colleagues who have played down south have encouraged him to take the next step.
I'd be more disappointed if a guy in his position wanted to play at Fir Park for his entire career.