Given Ferguson's track record of being out by orders of magnitude on absolutely everything beforehand, it almost seems like he was chosen to give an over the top estimate.
It would be comforting to believe that because it'd mean there were other epidemiologists who were right but ignored. Go read the works by his counterparts though, and they're all out by similar orders of magnitude.
It is possible. It is certainly common to pick the expert who says what you want them to - and to get rid of experts who say the "wrong thing" (e.g. the dismissal of UK govt drug policy advisor David Nutt).
