Other mistake: As the surviving characters discuss the fate of Westeros, 2 plastic water bottles can be seen tucked behind the chairs they're sitting on.
Continuity mistake: When the episode starts Arya is walking towards where Daenerys is and has her face covered in mud and soot, plus a long streak of dark dry blood running through the right side of her face. The next time we see her her face is cleaner and the blood is less noticeable. In further shots the amount of blood increases or decreases randomly. There doesn't seem to be much water and soap around the place.
Continuity mistake: During the meeting at the Dragonpit, Sansa is wearing her long silver chain and circle neckwear, with the long chain changing the way it is placed through the circle. First the chain is put through the circle in a way that's over and under, but in some shots the chain is put through the circle the opposite way, under and over. (00:53:10)
Visible crew/equipment: When Bran joins Tyrion and the others at the small council meeting, Bran begins by saying that they appear to be missing a Master of Whisperers, then just as he says, "And a Master of Laws," the boom mic can be seen dipping into view over Bran, at the top of the screen (visible on Hulu). (01:11:00)
Continuity mistake: When Grey Worm leads Tyrion to the Dragonpit, as they pass the column of Unsullied their long individual shadows are directly to their sides, but in the next shot the Unsullied are seen in the background and the shadows are entirely different. (00:46:00)
Continuity mistake: When Daenerys is dead she has blood underneath her back and hair, and as the camera is above her, her right arm is curved or bent a little. When Drogon picks her up her arm is now straight and despite the blood on the ground she seems to be completely clean. No blood on her back, hair or scarf. Then as Drogon flies away, how on earth did he pick her up with his left hind leg? Did he twist his leg 180° to pick her up with his front claw?
Continuity mistake: When Daenerys dies, in the close up her head is parallel to the ground, looking up at Jon. Cut to a wide shot and her head's hanging much further backwards, plus her eyes are suddenly closed.
Continuity mistake: When Dany dies, the blood trails coming from her mouth and nose are pale in some shots and dark in others. They also appear to change position slightly, but that might just be the camera angle.
Character mistake: Davos advises Grey Worm to claim land in the Reach and start his own house. Since Grey Worm is a eunuch, he cannot start his own house, as he cannot father children to pass his name and lands onto.
Answer: Basically it's because he broke his vow. A member of the Kingsguard is sworn to protect the king at all costs. Jaime elaborates more on the deed to both Catelyn Stark and Brienne of Tarth, telling Catelyn that no matter what course of action he took, he would be breaking one vow or another (i.e. if he obeyed the king, he would conversely be disobeying his own father), and telling Brienne that the Mad King was planning on burning all of King's Landing, but he did not bother to tell Ned Stark that. Ned Stark felt that killing Aerys was dishonorable and excessive. Robert Baratheon still could have usurped the throne without Aerys being killed.
Phaneron ★