The moon is a fragment of an ancient planet named Theia. It collided with earth and the molten remnants formed into a sphere by gravity. I'm pretty sure there isn't anything weird about the moon being circular like that. There are literally remnants of the planet sticking out of our crust and core of the planet recently mapped.

https://skyandtelescope.org/astronomy-news/bits-of-theia-might-be-in-earths-mantle/ The animation in this article show what I'm talking about.