In Doctor Strange, when Mordo and Wong are explaining to Strange about Dormammu and the Dark Dimension, they say he wants to devour all the worlds in all dimensions, and there is no world he wants more than Earth.
They never say why, though.
Do we have any information, preferably from the writers and producers, or if not, from the comics, explaining what makes Earth specifically so desirable a target? Wouldn't Asgard be yummier, for example?