Most of the "Vor v Zakone" (thieves-in-law) aren't actually Russian. Traditionally the vor underworld is dominated by criminals from the South Caucasus: mainly Georgians, Armenians, Azerbaijanis and Yazidis (from Georgia and Armenia).

The Russians always tended to have their own thing going on in the underworld and the well known Russian "Bratva" like Solntsevskaya, Izmaylovskaya, Podolskaya, Dolgoprudnenskaya and Tambovskaya were not controlled by criminals with a Vor-status.

Ukrainian organized crime - a lot of the "Jewish" organized crime from Soviet Union actually came from Ukraine like many of the mobs that were operating in Brighton Beach, the West Coast and West/Central Europe - also was always its own separate thing and had plenty of cooperation with the Russian mobs.

Chechens also always had their own thing going on that operated separate from the Vor structure. The major Chechen criminal clans like Tsentralnaya, Ostankinskaya and Avtomobilnaya were structured like extended crime clans that were based in certain parts of Moscow. Being as clannish and insular as they are the Vor culture was never immensely popular with Chechen gangsters.

Of course you also had/have thieves-in-law that are Russian, Jewish or Chechen but in general the number of Georgian, Armenian, Azerbaijani and Yezidi (whose number is disproportionately big seeing it's a relatively small community) thieves is overwhelming.