thorinds:

“Then the thought was, we still need to come up with a way to kill Azog and yet leave Thorin with a fatal injury, because it was important that he live long enough to have his final moment of reconciliation with Bilbo. I had the thought, ‘What if Thorin is using his weapon to block Azog, but Azog’s strength and weight was so great that Thorin realized his impalement was imminent?’ At that point he’d have to make a choice, which is great because it made it a character moment again. Thorin chose to withdraw his weapon and let Azog stab him, knowing that then his sword would be free to deliver the killing blow to the Orc. It would surprise Azog, who was busy delighting in his victory and never saw it coming, but it also mean that Thorin was sacrificing himself.” – Glenn Boswell (X)