Why is Karl Franz so popular?

I always see him in discussions and tierlists and youtube people say Reikland is the most popular faction in the game... but why?

I never played an empire campaign, and i completely understand why I'm the outsider for that, but what does the empire (and Karl Franz specifically) have that makes them more popular than other factions?

You could play lizardmen. Come on, they have huge dinosaurs! Or dwarfs, they have great artillery and almost all units have ridiculous armour, they are so hard to kill! You want magic? Go for the high elves, they even have great ranged units like the empire too! AND DRAGONS! Or what about the evil factions? There are vampires for crying out loud, and ogres and minotaurs and funky little ratmen with actual nuklear bombs!