Look at it from the US side of things. You have defeated Adolf Hitler and then went with the story he shot himself with the evidence basically all burned into unrecognition at the time that he shot himself and was burned. You then hang a bunch of war criminals who were in the mix. Yay! The world has avenged itself of them.
What is to be gained then years later telling the world, "Woops, we really let him get away and let him die at a ripe old age." By the time they figured it all out it was too late, so the best thing for them from a PR perspective is to keep going with the theory he shot himself in his bunker. On top of that, maybe you could be enriched by some of their loot that was offered if they could live their last years in the US, as well as any technological or espionage benefit to help fight the Russians. You would probably look at that as a win/win.
After all, when it comes to holding power the object is never justice, it is world dominance and control, which is why we see the current regime turn misdemeanors Trump has committed into felonies and the average Joe felonies into misdemeanors or pardon them all completely. Pun intended. It is also why Trump will not put behind bars all those who pulled that crap on him.
And without a willing media, how can the world ever know? Really it shows who well controlled they are by the state, which many figured out after how they treated Trump.