Why did David Milliband lose the leadership election?

Could it be because:

1. He comes across a little bit arrogant and aloof?
2. Supported by Tony Blair and people do want to the same old?
3. Is a bottler? Remember he had 3 opportunities to topple Brown but each time he backed off at the last minute. That makes him look like someone who cannot be ruthless and grab his chances. Who wants a timid leader?
4. The impression was that the Labour Leadership was his and perhaps many voters did not like being told that their vote wouldn't make much difference and as a result they voted for Ed as a protest?
5. Trade Unions!
6. He was just unlucky?

wow the reasons could be endless!!