Russia considers itself a democracy - apart from Putin being extended in term again and again, and opposition politicians and investigative journalists have a high rate of being killed by poisoning from unusual chemicals being put in their tea, or falling from bridges or windows in tall buildings. China seems have have become a post Communist state with everything based on the power and personality of Xi, and Iran sees the Uighurs as the wrong sort of Muslim, so they look the other way. All three reject the international system of rules in favour of 'might is right'. China has an insatiable appetite to natural resources, which Iran and Russia are happy to supply.
All three have problems with internal opposition to their regimes, which is one of the reasons they seek to find adversaries to distract their populations.