The Benanki claimed Earth as part of their empire and met with little resistance. This was because Edward Grainger, years earlier, had written his memoirs, titled My Life With The Doctor, and humanity gave up creating anything new, merely expecting the Doctor to help them in times of trouble. The Benanki provided food for the humans.
The Seventh Doctor prevented this from happening by going back and convincing Edward not to write his memoirs. (PROSE: Testament)