> if the crust is sturdy enough In short, the crust is not sturdy enough. In comparison to the bulk of the earth, the crust is like the film of dry paint that

> if the crust is sturdy enough In short, the crust is not sturdy enough. In comparison to the bulk of the earth, the crust is like the film of dry paint that forms on a paint bucket if you leave out too long. At the scale of a planet any rock is still a liquid for mechanical purposes. (Which is in fact what the hydrostatic equilibrium part of the IAU definition of a planet is talking about.)