The big reason Game of Thrones is such vibrant fodder for theorizing, Reddit-enabled whizkids is that creators D.B. Weiss and David Benioff, working off George R.R. Martin's completed-but-not-yet-published crib sheet, can foreshadow like only a Three-Eyed Raven could. They know the past, present, and future, and scenes from years ago can be recalled at a moment's notice in Season 7 for sweet payoff. Expect the ending of the entire series to be one big setup event. Hell, even Joffrey's death way back in Season 4 can return as the perfect callback.
For those with a keen sense of Westeros history (or those of us who spend way too much time down the Game of Thrones rabbit hole), the final beat of episode 3, "The Queen's Justice," connected the dots of Weiss and Benioff's clever plotting and gifted legendary actress Diana Rigg the send-off she deserves for her no-bullshit performance as Olenna Tyrell. How you die with dignity on Thrones: reveal you're the mastermind behind one of the greatest deaths in seven seasons of mayhem.
The setup: Instead of defending the Lannister homestead of Casterly Rock (which everyone expected), Jaime (Nikolaj Coster-Waldau) and his battalion made their way to Highgarden, home of the backstabbing Tyrells. Slaying the meek troops without breaking a sweat, Jaime makes his way to the castle's main chambers, where he finds Olenna, seated and ready to die. They exchange the kind pleasantries, Olenna pleads the Kingslayer to wake the hell up that his sister is a grade-A psychopath, and then both figures in this episode-capping chamber piece turn to the matter at hand. Instead of decapitating Olenna and dragging her bleeding corpse through the streets of King's Landing, Jaime's offered the aging matriarch a distinguished demise: a sip of poisoned wine.