First lets address the 800 pound gorilla in the room when it comes to the Russian mob; It’s actually the Russian Jewish/Lithuanian mob. Virtually the entire leadership of the Russian factions in the Midwest are Jewish/Lithuanian, or both. I have no reason to believe this is not the case everywhere.
The reason they have become a priority is simple, it is the nature of the rackets they trend to.
Gun running, Human trafficking, White slavery, International Prostitution Medicare, Medicaid and welfare fraud, Section 8 Fraud, Identity theft, Cyber crimes, “Dumping” or property of cities and counties, all orchestrated from 3 Continents meaning it is not just racketeering but international racketeering, meaning that agencies outside the US become involved.