Amusing [VIDEO]
There's oversight, it's just difficult to get it applied to prominent individuals (ask Trump) in any system that doesn't formally prioritize such.
Summary: The South Dakota attorney general ran over a pedestrian lethally in the middle of the night, hit and ran (the victim's glasses were blown into his car), tried to brush it off as a misunderstanding or the result of the victim's intoxication or suicidality.
The AG was not indicted as a normal person would have been, but there was an expectation that he would resign. He did not resign and now is running for reelection, creating the scintilla of a possibility that his own party (one guess which) will impeach him in the near future.
What more "oversight" is needed in a clear-cut case of negligent homicide that state police thoroughly documented? Governmental actors need to have a willingness to 'pull the trigger' is all. It seems to me primarily a matter of creating incentive structures for the scalps of politicians and magnates...
Last year Mexico held a symbolic referendum on whether former presidents can be prosecuted for corruption. It won with 98% of the vote with 7% turnout. That seems perfectly representative of the underlying issue.