Normally the trunk has some pretty good taper when water is much less often and so it will stand upright when it goes through these periodic wet and extended dry cycles. When it grows slowly due to infrequent watering the trunk does not get spindly and fall over.
In wetter climates this has been a problem with this plant when it gets about 5 feet tall. When water is present all the time it will take advantage of the excess water and grow as much as it can in length and not in girth. It gets top heavy and topples over.
It wants to reproduce and it does not care if it is upright or laying on the ground to do that. In fact, it is possible it could root from the trunk into the soil as it is lying there. This plant can root from trunk cuttings when propagating it.
If you don’t like it lying on the ground then cut it off close to soil level and leave those “pups” at the base to grow into a clump or you can divide them in the fall, or even now, if you are quick about it.