Oh, no no. [He shakes his head, waving a hand for emphasis.] You're thinking too small. A truly megalomaniacal villain seeks to gain the unerring adoration of the people. How better to do so than to first dupe some unsuspecting hero into flitting about through time to muck things up nearly irrevocably, but retain just enough of the knowledge to undo their folly, thus seizing all the credit both for averting the apocalypse you helped to orchestrate and the undying faith of the unwashed masses?