Of all the major waves of immigrants to the U.S., the germans seem to have produced the fewest gangs/organized crime groups. I'm sure part of this is because a german immigrant was less likely to settle in a dense ethnic enclave within a major city than say an Italian, but there were quite a few predominantly german neighborhoods in New York, Chicago, Pittsburgh, etc. So what's the deal?
It's hard to say something didn't happen, but we can say why other groups did turn to organized crime. Ethnic groups who were blocked from traditional employment often attempt to break out and make it by turning to crime. We can see this in the heavily discriminated against groups of the Italians, Irish, Jews, and Black organized crime, but not in the generally accepted Germans.