You really don't get it. Evil Lords "want" to be defeated. Just think about it. How long can he keep the things going?
The villages dried out by crazy taxes. The abused mines, with countless deaths to get as much ores as possible. The corrupted government full of incompetent creeps so dumb to actually belive your evil-messiah agendas. The psyco army guards out for blood who you can barely keep in check by letting them go wild on the poor in the slums. Everything is falling apart.
So, when a party of promising idealistic good guys start a quest to get your head, you let them do their thing. Hell, you even toss a lead here and there to get them on the good track. And when they finally reach you, everything goes out with a big BANG!! And Evil Lord is no more.
Then. Some times later, somewhere far-away. A mysterious carriage fully guarded and fully loaded with gold and jewels, quietly leave the kingdom. Undisturbed and unchecked.
Purrrrrrrrfect ๐