On a scale of how far their gravity well extends to suck things up, Saturn and Jupiter are both like the vacuums of the solar system, collecting long period orbit rocks and rubble piles.

https://en.wikipedia.org/wiki/Hill_sphere

Some of these moons are smaller than the asteroid that killed the dinosaurs.

Hypothetically*

The crater isn't hypothetical:

https://en.wikipedia.org/wiki/Chicxulub_crater