Simple... You all started celebrating too early, got cocky, didn't play the ball up the the field the whole 2nd half, got lazy towards the end, with sloppy defence conceding a free kick which Zidane promptly scored. And Gerrard who is usually a very good passer of the ball made a huge mistake passing it back to James, and the PK was set. Hope this solves your question.
Cheers,