The full extent of the Reunited Kingdom

[Inziladun]

Originally Posted by Rhun charioteer

Why would Gondor have been rotten morally or otherwise?

In The New Shadow, as Kuru notes, people in Minas Tirith were basically forgetting what it was like to have lived with the fear of Mordor. Boys were running around being vandals, pretending they were Orcs. And this was in the reign of Eldarion, Aragorn's son. Like Men of any level of nobility or virtue, they soon grew tired of peace and stability. As high as the Númenórean remnant of Gondor were, as time went on they would inevitably become more like other Men of Middle-earth, with their history as Edain receding into dim memory.

I think it might have taken quite a while for them to have developed any 'imperial' designs for their neighbors, but a greedy King coupled with a dissatisfied populace could have started things up.