This is a flawed analogy on many levels. Disney isn't in the business of gambling for entertainment. They are making business decisions. Perhaps a better analogy would be "If a casino lost 1/100th of it's net value in one night to several customers on a winning streak, it would not be a serious threat to the casino's health, but the manager would lose his job before the next day's sun set." It indicates a serious flaw in the implementation of the casino's business strategy.
Prequel has nothing at all to do with the validity of the train of thought. Studios make movies with the intention of making a profit. How much of a profit depends on the movie. Some movies are even made with the intent that they will make so much money that they offset the failures. When that type of movie is itself a failure, its a serious problem on many levels.
That's why we're not likely to see any more "A Star Wars Story" movies. The movie made money, but not nearly enough. It didn't do its job.
Under performing, whether in Star Wars, the MCU, or the DCEU, is a always a very big deal.