Obviously with gambling, it's more stochastic in nature by design but often large complex processes have a lot of stochastic elements to their successes and failures as well.
another key difference is that the expected value of a bet in gambling is less than or equal to zero (depending on house cut). the expected value of a single stock is unknown (at least to a retail investor), but the expected value of a broad portfolio is positive in a growing economy. you can "lose" relative to others and still be better off than if you had not participated.
it's certainly possible to gamble with stocks and derivatives, but in general, investing and even speculating are not necessarily gambling. imo the difference is in the strategy behind the trades. though wildly risky, speculation can be rational when backed by an advantage in information and/or analysis. a retail investor watching daily prices and backfitting a narrative from news stories is not an example of a rational trading strategy.
Gambling is taking on a risk to get a reward - the risk isn't offloaded by somebody else. It's set by the house.
For example, horse race betting, roulette, or blackjack, is gambling, not speculating. Betting on commodities futures is speculating, not gambling - commodities futures is one way a producer can offload future price fluctuations/risk to somebody else (who "wins"/"loses" if the prices rise/falls).
"Oh, well, no. Neddy doesn't believe in insurance. He considers it a form of gambling."