Moses descended the mountain to tell everyone "There was a bush on fire that made some great points!" and it somehow worked.
The Non-Miraculous Explanation:
Know what else burns forever without disintegrating? Charcoal! Not your average Kingsford bag (half-used from last summer, in the shed, full of earwigs), but a more exotic, naturally occurring kind of fuel. The burning bush may well have been a bunch of acacia plants, which are known for making great charcoal. In all probability, the framework of the bush stayed in place, making it seem like it was burning endlessly.
"Moses! Do ... do 20 jumping jacks! I don't know! I'm running out of tasks! Moses! Shave the cat!"
Why did it spontaneously burst into flame in the first place? Well, scholars have long claimed that Mount Sinai (Moses' favorite hideout) was an active volcano back in the day, which is generally a pretty flammable place. Is the idea of an acacia bush sitting on the mouth of a volcanic vent that far-fetched?
As far as how the bush was able to verbally introduce itself, Benny Shanon, a researcher at Hebrew University of Jerusalem, posits that there are two plants near Sinai -- including our friend the acacia -- that have the same psychoactive molecules as ayahuasca, which is known to produce overwhelming religious experiences, like hearing voices and meeting God. Yep, that's right: Moses was maybe just high. Look who's surprised! It's our good friend, Nobody.
When he finally came down, we guess Moses doubled down and rolled with it.