The assassination of a president or other major political figure is quite a bit different than a DA in a corrupt city turns out to have some skeletons in his closet. He wasn't a JFK or a MLK a leader in national or world-wide politics that paved the way for a huge change in the way people acted or thought.
He was the DA in one of the most corrupt cities in the world. Hardly a blip on anyone's radar outside of Gotham and after eight-years probably not even regarded much. On a local, city-wide scale the circumstances around the death of DA isn't news anymore after 8 years. That his death was covered up and lied about a bit, yeah, that might get a few people's interested piqued a bit but it wouldn't be too big of an incident.
Hell, look at New York and Charlie Rangel a man who is
corrupt, was censured
for it by Congress and the city of New York still didn't care and re-elected him anyway.
I doubt a little scandal about a DA is going to be blip on the pubiic's radar after eight years especially in this day and age.