The size of the market was vastly overestimated. Every pothead wanted a slice of the business, so they all started up companies thinking there was unlimited growth potential. It was rapidly saturated and now we’re in the collapse and consolidation phase, exacerbated by the higher interest rates and inflation.
Canada’s population is similar to California, but it’s producing weed enough for a country several times its size.
Plus the black market still exists, albeit in a small scope, due to price, quality, variety, or loyalty reasons.