This happens all too often in the women's races, this year and last year it was Morgan, before that it was Gelete Burka the year she was the clear favourite, the line goes back to Decker-Slaney and possibly longer, every championship it's someone in one or more of all the finals. If you are or think you are the best then take it from the front like Rudisha did in the 800s and the way El Gerrouch did when he was at his best.
Hmm... In all fairness, El Gerroch did fall the same way in his first Olympic final, I remember him saying that motivated him to go on for another four years and train even harder so that he would be able to run it all the way from the front the way he then came to do.