Why did Luis Enrique move from Madrid to Barca for free?

Luis Enrique didn't like changing Madrid for Barcelona, but the opposite. Luis Enrique was at Real Madrid for 5 seasons and more at Barcelona. He generated debate and a lot of criticism, of course.
In a conversation for 'Colgados del aro', the current Spain manager told the reason why he didn't stay at Real Madrid.
"I ended my contract with Madrid after five years and we didn't reach an agreement to continue. They wanted to renew but there was no agreement. From then on, I took the path I decided on," he said.
The ex-CM wasn't surprised by the reactions there were when he signed for the eternal rival. In fact, Luis Enrique urges this kind of transfer.
"You don't generate hate. That's a release of hormones that you have in there. You have to encourage more team players to change. It was gratifying that Capello said he couldn't understand me leaving for free", he continued.
About his controversial celebration while at Barcelona, Luis Enrique explained that it was not about anything, but simply about the goal: "For one that I score, you have to celebrate".