In the books we read about marvelous feats of dark magic done by poweful dark wizards other than Voldemort -like the deeds of Herpo the Foul who created Horcruxes or Salazar Slytherin who made the Chamber of Secrets.

So, there were some other dark wizards of great power.

Is there any evidence that they tried to conquer the world?

If not, why wouldn't they try? Or why would these tries be concealed?