I get the sense from you that you believe that the left-wing candidates were either tried, convicted, and banned from running in the past without media attention, or they are pure as the wind-driven snow and only the right-wing candidates are corrupt.
I think the left-wing candidates are "strongmen" and are of a government that is preventing opposition by any means possible.
President Trump was too big to rig by our entrenched left (though they tried and tried and tried), but these others in Europe and South America are not so lucky and are getting kicked off of ballots when they become too popular.
-PJ
As I noted earlier in the discussion, there are simply too many variables.