Lets commence with a little background: In 1780 England adopted the Diplomatic Privileges Act. This act granted total immunity from both criminal prosecution as well as civil suits, so that ambassadors and their families could exercise the native country’s diplomatic mail, without fear of repercussions from the host country.
In fact, the institution of diplomatic immunity was, even then, so respected, that the government could prosecute an individual initiating a lawsuit or bringing charges against a diplomat. Why do countries and non-governmental bodies grant diplomatic status, and therefore, immunity, should the eledged provide a useful service for them. It could be that this “useful service” is as simple as giving the right amount of money to the right people.
Several organizations, such as SDG, The Holy See of Antioch and the Sovereign Military Order of Malta (SMOM) can arrange diplomatic appointments for individuals with clean criminal records, and who would prove useful to a country’s diplomatic service.