In this sentence I can't imagine any reason why he should have behaved in such an extraordinary way, did
I can't imagine any reason why he should have behaved in such an extraordinary way
Did he behave or did he not behave in an extraordinary way? If
If he did, why the author didn't simply say, "...why he behaved..." instead instead of "...why he should have behaved..." ?
It is not clear to me why the author has used this tense rather than past simple.