The vicissitudes of life bring about all sorts of mishaps. In the existence of a Crassula arborescens plant this may include more than the natural discarding of dry leaves disappearing from lower stem parts.
Live leaves and even branches will break from the plant through contact with an outside party invading its space; or perhaps from a strong wind or a weak connection. Such succulent parts can survive on the ground long enough for adventitious roots to be grown. This will start an independent plant vegetatively as if planted from a cutting. Adventitious means here that these roots grew from an organ other than the actual root system of the plant, i.e. typically from a leaf or stem.
The collection of dry bark rings in the photo indicates the remains of a large, multi-stemmed C. arborescens plant (or several plants living very close together) that had occupied this space for a long time.
Before its (or their) demise, small bits had dropped off, starting at least three new plants as a belt and braces enhancement of the probability of producing sufficient offspring. This is a last gasp additional contribution to species survival, on top of all the seeds set from all the flowers over all the years.
Life exists because living things that cannot think about it do their very best to reproduce. People can think about it, sometimes decide not to, but just see how much they have multiplied!