Transnistria was created by a pro-Soviet rebellion, at a point where the Russian government was on the verge of collapse. It has a significantly higher living standard than Moldova, one of the worst nations in Europe, which its citizens do not want to join.

It wasn't formed by massive arms deals and covert invasion followed by actual invasion like Ukraine's separatists. The Russian 'volunteers' were defectors with ethnic ties to the nation, who became fugitives until the Russian legal system collapsed completely, and illegal paramilitaries.