Subsurface mass concentrations (mascons) perturb orbital eccentricity across the Moon until satellites outside 4 frozen inclinations crash into the regolith within months:

At the same scale, the Moon's geoid height (−540 to +571m on the GRAIL GRGM1200B model) is nearly 6x lumpier than Earth's (−107 to +86m): very uneven gravity is why almost all low lunar orbits are unstable, making low lunar orbit a self-cleaning orbit.