Actually they were. They felt the end of the world/the return of Christ was imminent and so why bother?
Yeah, I’m not sure about that. Constantine, Justinian, Charlemagne—all Christians who fought to restore the Roman Empire (really a quite different Empire in the case of the latter) to its former glory.
Churchmen might have been more pacifist than they were during the Crusades, but I think the immorality of the late Empire had much more to do with it.