Lambert did the same thing to Colchester - jumped ship for a bigger job. Norwich fans must be disappointed, but they can't hold it against Lambert because he has obviously got ambition, just no loyalty. A season treading water with Norwich was not going to improve the CV, and there will be significantly more opportunities to change things at Villa as they can improve on a really terrible season just by changing the players attitudes and some tweaking of the existing squad. Any player investment will be significantly higher than Norwich will be making so I can see exactly why he's gone.
With what Lambert has done for them, do you really not think he's not entitled to have a little personal ambition..? With the best will in the world, Norwich are never going to progress much further than they already have. With all respect to Norwich City, they have been, and remain a stable club in a similar vein to Saints before our relegations and our present owners came in. Although they haven't done it for decades, Aston Villa are a former multiple League winning club, who will feel that European football should not be beyond their capabilities, and eventually higher still.