Strange they didn't create an Ashkenazi ethnic group. If they had you would have seen most of those numbers for Latvians, Lithuanians and Russians migrate to the Ashkenazi category.
For two thousand years they had no country to fight for or protect them, and as a tiny minority in a Christian Europe, physical resistance meant annihilation, but they certainly know about social cohesiveness and how to organize and get what they want. People forget, but there was a Jewish Mafia very intertwined with the Italian one and an Irish one as well, but they never had the success of the Italian Mafia, for lots of reasons which really don't pertain to this topic.
The Italian Mafia was ultimately brought down starting with Robert F. Kennedy, who didn't investigate the Irish mob with which his father was affiliated, or the Jewish mob, but the Italian mob. The decay of the value of omerta' among Italian-American members, leading to snitches like Valachi and then the passing of the very probably unconstitutional RICO statues ultimately did them in. By the end what you had left were men like that joke and media hound Gotti and the rat snitch and predator on women Sammy Gravano. I mean, they're all depraved men doing terrible things like extortion, running prostitution rings etc. as well as institutionalizing gambling and trafficking drugs and doing deals with businesses, but the prior generation, the ones from Italy, had some gravitas and honor amongst themselves in that they didn't betray the organization, even if they regularly killed their own bosses to take over the organization. Psychopaths, a number of them, but they kept within certain limits.
Back to topic...apologies for the digression.
I'm sorry to disagree slightly with your premise, but I don't think violence is the determinative element. There are violent men and criminals in every society on earth. The thing is that if they come from cultures where people know how to organize one another in groups to achieve goals, there is some measure of intellect at least in the top men, and an ethic of hard work to achieve those goals, loyalty to the group, keeping your word within the group, then if they have to or want to turn to violent crime, they will master it.
Both the Italian Mafia and the Yakuza are examples, although the Italian Mafia in reality no longer really exists as it once did.