Super Duper Spoilery Of Course
The pictures that Sam laid down as his last card, the pictures of their mother and them as babies, those pictures served the same function as the Impala/Green Army Guy did for Sam when he was fighting to regain control from Lucifer. The pictures triggered Dean to remember why his life has mattered, because of the love he’s had his whole life with his family.
That was how Sam saved Dean.
That was why the Js were comparing this episode to Swan Song. One brother reminded the other of why they’re still bothering to stay around:
This crazy, painful, awful life that they’ve shared, pulling and pushing each other along, surviving together, saving each other, being there for the other when he’s broken, that’s what’s important.
That’s what’s worth breaking the world for.