The likely explanation can be found by looking at the Roche limit for those objects with crater chains. This is the distance between objects where a smaller body, say a comet, gets closer and closer whereupon the tidal stress by the massive primary object (Moon) is enough to rip the comet apart. Thus a string of objects (debris chunks) form in roughly a straight line before impacting the surface.

This, surprisingly, has been observed. Here is a comet that broke-up, formed a string of objects, then impacted and bruised Jupiter...

Shoemaker-Levy 9
The equation for the Roche limit (distance at the point of breakup) is fairly simple. But there is more than one Roche limit. The first is a fluid limit where the simplest example is one where the object is a fluid, thus easier to break apart and would have the farthest Roche limit. But objects aren't fluids and their internal tensile strength must be taken into account. The greater its internal strength, the closer it can get to the larger mass before becoming torn by the tidal stress. Recall that tidal stress is an inverse cube of the distance relation, so a little change in distance makes a big change in stress.

Phobos, moon of Mars, is nearing the fluid Roche limit, but it likely has another 10 million years before the tidal stress gets the best of it.