so ... what happened? [spoilers, obviously]

This film is streaming on Netflix so I can re-watch as much as I want, but I still can't figure out exactly what happened to the three guys who fell. Can some nice person who understands climbing or is more observant than me (or has read the book) please explain?

Regarding red-helmet:

In the moment prior to the loosening of the piton, he seems to be under his own weight on a slope that isn't close to being vertical, and his line isn't taught. A few moments before, Eastwood loses his footing on a similar slope and easily catches himself.

Regarding white-helmet:

As red-helmet is falling, white-helmet yells "I can't hold him!" But when red-helmet goes over the edge, his rope isn't taught, suggesting he isn't pulling white-helmet. Did he pull white-helmet free, and then white-helmet let go, but too late? Or is that non-taught line a goof? And why does white-helmet's piton come loose so easily? Note that it comes loose as red-helmet is early in his slide, and it's a full-body slide down a not-that-steep slope -- in other words, the situation isn't even remotely comparable to situations in which people fall and are dangling but the piton holds. Red-helmet yelled "The ice is cracking!" as he was falling -- is that what explains it? Was there a reason to expect the ice would crack in that way? Was the piton loosened from the earlier fall? If so, why the hell wasn't he spending his time hammering in a new one?

Regarding Eastwood:

He gets knocked of the cliff by blue-helmet's dead body. But why did that happen? He was right next a very secure piton (secure enough for him to fall and dangle from), and he isn't connected by rope to blue-helmet's body, since blue-helmet falls over the edge. Moreover, he had plenty of time to see what was going on and hold on. So are we to believe that he was knocked loose by a dead body? That seems odd. In the situation he was in it should have been easy to hold on and let the body glance off him.