Weed is incredibly easy to grow and consumers simply cannot consume all that much of it. Half of all weed users like the idea of investing in weed industries. Too much investor money chasing a small TAM.
I buy that it's ~500x harder to grow 500 plants than 1 plant. But on a per plant basis, it is very very easy. And at scale you would do even less work per-plant than people trying to maximize a single plant.