Could you please explain why Uranus is laying/spinning on its side?

The reason for Uranus' tilt is still a big mystery. Most astronomers do not believe that the planet formed this way and was instead knocked on its side by an impact in its early history. The collision could have been with any object large enough to cause the tilt. However there are still a few questions this theory does not answer. For instance, why does Uranus still have a nearly circular orbit like most of the other planets if it was knocked so hard? And if its moons were formed before the collision, why are their orbits also so nearly circular?