When California voters legalized recreational marijuana with the passage of Proposition 64 in 2016, the move caught the attention of big-money investors from around the globe. Eager to reap the rewards of what would become the world’s largest market for regulated cannabis at the time, speculators poured untold amounts of cash into the state to stake their claim. But while Prop. 64 created new opportunities for adult-use cannabis, it also upended an existing medical marijuana…