>> What ‘crap’ was he talking about? <<
I don’t think a distinction as to the exact nature of the referenced “crap” is material to the argument at hand. Not worth quibbling over. I believe the embedded message of Trump’s rhetorical question is invariant, as it were, to the specificity of the excrement.
On the other hand, the whole incident clearly doesn’t matter because Trump can do no wrong. Nothing to see here. Move along.
It is absolutely material to Trump’s comment. He was talking about the knife breaking just at the moment Carson was stabbing someone, as Carson told the story.
That is what Trump said was crap.
That is what he said was unbelievable. That is what Trump said he didn’t think Iowans were stupid enough to believe.