Other mistake: In the beginning of the movie, the radio announcer says it is 74 degrees with a high of 89 degrees expected. The guy directing the oil truck breath is visible and is wearing a winter coat, not very likely at that temperature. People walking the streets are too heavily dressed also.
Other mistake: In the restaurant scene with Scylla (Doc), Babe and Elsa, Scylla pontificates, briefly, about wine and then orders a Chablis Grand Cru (which you don't need to be a wine buff to know is a classic white wine). However, the wine they are drinking, a few minutes later, is a red.
Answer: The diamonds were "blood money" that were stolen at the expense of many Jewish lives during the holocaust and also resulted in Babe's brother, "Doc" being murdered. For that reason, Babe would not want them, nor would he allow others to profit from them. Szell needed to risk being recognized in New York in order to retrieve the entire cache of diamonds from the bank safe deposit box after his brother, Klaus, was killed. Klaus would retrieve as many diamonds as Szell needed to sell to support himself in South America. Once Klaus was dead, no-one else could gain access to them for Szell, or if they could, probably would have stolen them.
raywest ★