Ethan Hunt: Can I ask you something, Kittridge? If you're dealing with a man who has crushed, shot, stabbed, and detonated five members of his own IMF team, how devastated do you think you're gonna make him by hauling Mom and Uncle Donald down to the county courthouse?
Jim Phelps: Of course he knew. Just when he knew is something of a mystery. You mind telling me, Ethan? Was it before or after I showed up in London?
Ethan Hunt: Before London. But after you took the Bible from the Drake Hotel in Chicago.
Jim Phelps: They stamped it, didn't they? Those damn Gideons.
Jim Phelps: We're being ambushed Ethan. Abort! That's an order.
Ethan Hunt: Negative. Golitsyn is on the move.
Jim Phelps: No, dammit, I said abort.
Ethan Hunt: Eye on the package. Jim, I'm Coming.
Franz Krieger: Try any sleight of hand with my money and I'll cut your throat.
Senator John Waltzer: We were living in a democracy the last time I checked.
Franz Krieger: If we're going to Virginia why don't we drop by Fort Knox? I could fly a helicopter through the lobby and set it down right inside the vault. And it would be a hell of a lot easier than breaking into the goddamn CIA.
Ethan Hunt: I thought I was going to see Max.
Matthias: You misunderstood. No one sees Max.
Ethan Hunt: Then what am I doing here?
Matthias: Allowing Max to see you and hear what you've got to say.
Ethan Hunt: I don't communicate very well through a shroud.
Matthias: If Max doesn't like what you have to say, you will be wearing that shroud indefinitely.
Answer: I disagree with the other answers. I watched it in slow motion and thought he was going for the kill. There would be minimal struggle since Ethan isn't in a fighting position and Krieger was inches from his throat with the knife before he dropped it. He wouldn't care if there's a lock down because he would be out by the time they notice Ethan's body above. I guess blood spilling would give it away, but he'd still be out and under cover before anything can be done. He doesn't have to know who Max is or how to contact her he's working with Claire and Phelps. Luther wouldn't care too much because he just met them. At most all they have to say is that there was an accident and Ethan didn't make it. Max wouldn't care because she just wants the real list. If Ethan dies early the bad guys win and IMF will think hey he was the mole and got double crossed. There is 0 reason for Krieger to not kill him at that moment. He has the disc and that's all he needs.
Job as Jim lost confidence of Max. The deal was with Ethan. Ethan had to survive.