Why was Dr Robotnik's name changed to Dr Eggman in Sonic the Hedgehog?

When I was a kid I used to love the original animated series of Sonic the Hedgehog. Most of the animated series’ airing in the 90’s referred to the evil villain as Dr Robotnik (sometimes Dr Julian Robotnik)

Then years later they come out with this series called “Sonic X”; which is a little too like Pokemon in my view. Anyway they changed his name to Dr Eggman. Why would they do this?