Article misses the point (perhaps due to their capital investments) that the resurgence in active trading is almost entirely just gambling, but exempted from casino regulation. Also, saying "no more" to refer to a blip fad is a ridiculous healdit.
except it isn't: if enough gamblers stick to one ticker, they can break the market. options aren't roulette and stocks aren't blackjack. casinos don't have this failure mode. gamestop was the example of what happens in the limit - only the DTCC prevented a global financial crisis as a circuit breaker of last resort.
Casinos need to ensure that they have enough liquidity to withstand a large bet hitting. The law of large numbers only works if you can survive the short term swings.