"Tried" Mason killed JFK. They took it out of the game for controversial reasons, but thats what happened lore wise, and they nod at it with that response by dragovich.
When I first saw the ending, I thought, "oh creepy, Mason killed JFK." But at the time, I thought the assassination happened after all the events of the game, which makes it a bit of a downer ending after that great victory against the Nova 6 project. Then after learning more about the dates and historical events of the game, I realized that JFK was assassinated midway through the game's story (he died before the Vietnam War really took off). That makes Hudson's line ("there are gaps in your memory. Times when you went MIA and we couldn't account for you.") even more ominous because in the game's second half, your allies have no idea that they're fighting alongside JFK's killer
That ending scene breaks my heart. I remember playing BO2, during the opening for the invasion of Panama mission when you're playing as Frank. They all get together at McKnight's house on base. McKnight makes the comment that he read Mason's file and asks him if "all that shit with the numbers" was really true. And Mason gave some blow-it-off type answer about how the Russians "tried", as though he was sort of being funny about it; "yeah, they tried, but it didn't work" type shit. He had no idea. No clue. Imagine for a moment, being him; you spend the rest of your days not knowing that you were responsible for the most heinous and controversial assassination in modern American history... and you didn't even know. This scene where they show him in Dallas, the way he just brutally murders Dragovich after he he says "...tried?", and of course, Kravchencko's Afghanistan interrogation. I wonder if Mason ever figured it out. Maybe he DID know... and he didn't want to ever admit it to himself because Hudson already told him that Resnov sabotaged the brainwashing before he could carry out the assassination. Idk man this game has got me thinkin' way too hard 😂 Still, Mason is a tragic af character