For asteroids about 100 meters [328 feet] in diameter collisions are not the primarily cause of break ups -- rapid rotation is," the Smithsonian Astrophysical Observatory stated. Moreover, because the rate of collisions depends on the numbers and sizes of objects but rotation does not, their results are in strong disagreement with previous models of collisionally-produced small asteroids.IOW, small bodies acquire spin directly or indirectly through solar energy, and fly apart. Of course, this doesn't explain the fact that asteroids studied up close appear to be made up of at least several smaller bodies in the first place. :')
A lot of asteroids have “moons”, smaller bodies orbiting, which would seem to indicate they are massive enough to be gravitationally bonded. Saturn’s moonlets embedded in its rings are held together by tensile strength, tidal forces are not strong enough to tear them apart.
Clearly, anything outside the orbit of Mercury is outside the Sun’s “Roche Limit”, meaning that gravitationally bound bodies can form, orbitally induced tides are smaller than gravity. A particle is gravitationally bound to a larger body if the gravitational force is greater than the centripetal force. Spin anything fast enough and it will fly apart.