Continuity mistake: When Jorah gets his royal pardon, the wax seal is hanging freely. Camera changes and now the wax seal is resting on his fingers. (00:31:00)
Continuity mistake: When Jon and the others emerge onto the other side of the wall, there are 4 people with torches. Pay attention to the one at the back on the screen left. He has his torch in his left hand in this shot, but as the shot changes to the front he now has his torch in his right hand. (00:44:30)
Continuity mistake: When the group of men emerge at the other side of the wall, the last man with a torch has it held vertically. Camera cuts and now it is held at around a 45 degree angle. (00:44:30)
Continuity mistake: When Jon is taking his vow at the tree, the red markings on the tree change between shots. 2 single lines become joined, and a third single line becomes less smudged. (00:45:00)
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 ★