but, need some "tweaking" to even start considering your questions:

So what happened here? What about his character was missed? Can modern officer and soldier selection select out for this?
"here" and "his" being Singapore and Percival; "there" (my word) being the Canal (and Chosin) and Puller.

Put another way, what made the 1st Marine Division special ? Answer: nothing; they were just Marines.

Regards

Mike