Some thoughts from a book reader.
1. Jon was brought back just like Beric Dondarrion. The Lord of Light was not done with him yet. In the books I'd imagine GRRM is going with Jon is Azor Ahai reborn, the one Melisandre thought Stannis was from her vision. In the books when she looks into the flames to see Azor Ahai's identity, she sees only snow. The show needed him to be the bridge between Dany and the North folk. Plus they needed that hot incest action and a vehicle to drive a wedge between Sansa and the rest of Westeros.
2. Brienne is clearly the most noble character on the show. She's always been about keeping her word and her ideals as to what a knight should be. Jaime is the reality of what a knight is in Westeros. They're fairly shitty people. I honestly didn't mind Jaime going back to Cersei. He's seen what Dany can do. He knew what was coming for Cersei and he couldn't keep away. He wanted to die in the arms of the woman he loved, just like he told Bronn way back when.
3. He was going to fight for the living because he saw what they were up against. Then when he lived and humanity was saved, he went right back to the woman who brought out the worst in him. I agree his character arc was badly mangled but I doubt it's that far off from what GRRM had in mind. Jaime was trying to be good but he's still a Lannister.
4. It was all about her getting her comeuppance through the death of her children, the people she cared about the most in this world. For the people who hated the way she went out, she went out seeing everything she had built be destroyed because of her own arrogance. That's after watching or being a participant in every one of her children's demise due to her scheming/hunger for power. She died numerous times on the show.
5. To show how much Ned Stark loved his family. He went through the whole lie because he loved his sister and he made a promise. He never spoke the truth of Jon's birth because he knew what that would mean to the Kingdom and how he would place his family over King Robert. And it came at a great cost to his honor. Plus it adds the whole forbidden element to him and Dany. Of course, that's now out the window and Jon is a threat to Dany's rule.
6. Cersei is never more dangerous than when she's fighting for her children. I think it was also to force Jaime to stay. But Jaime never cared about his children. Or it was all a lie.
7. The Night King was a wholly D&D manufactured character. I highly doubt GRRM even has him in there. The show apparently needed a Big Bad according to D&D. First, it was Ramsey. Then the Night King. Now Dany.
8. In the books, Craster's sons are just given to the Others as an offering. The show created this idea that the sons later become the Night King's lieutenants, capable of independent action from the wights the NK controlled.
9. Because everything is too accelerated. Why they went with 6 episodes is beyond me. I am very curious how they wrap it all up tonight.
