Since it was formed from swirling matter, it just kept moving in the same kind of spinning motion. As for the direction, there is no real reason the Earth has to be spinning the wa y it is. If Earth were spinning the other way, we would just have sunrise in the West and sunset in the East. Because the rotation of the Earth is toward the east, the plane going against the rotation, or the plane going west, would return to the airport sooner. As far as 'balancing it out'.
Mountains have little or no effect on the rotation of the Earth.
Compared to the diameter of the Earth, mountains are no more than a roughness on the surface. If you look at a textured globe, you can see and feel that the mountains are no more than small bumps compared to the Earth. At what earth rotational speed we will be thrown off into space, i.e. gravity can't keep us here on earth. In order to throw us off the Earth at the equator, that is, to completely overcome the effects of gravity there, the Earth would have to rotate 806.4 times every day. I live in New England.