His expected outcome was in his favor because he whittled the house edge down to nearly even odds, and he had loss protection of 20%. But you're right that that

His expected outcome was in his favor because he whittled the house edge down to nearly even odds, and he had loss protection of 20%. But you're right that that didn't come into play because the actual outcome happened to be in his favor and ballooned out of control thanks to a random walk.