I have no idea how technology makes this possible, or if it just takes weeks of watching Brian Williams footage and waiting for him to say the words you need. I imagine a job like this takes hundreds of people. You give them each one word, tell them all to go watch Brian Williams footage until their word shows up. Then you play the waiting game. The diligent word-hunters take note of when and where their word finally popped up, then they fill out a slip, hand it in to the video editors, and they get to splicing and pasting.
However it’s done, the results of this one are perfect.