Could it be they were all focused on other things and simply didn't observe him? Many people simply do not notice things or people that are close to them and many also simply do not recollect information.
_Correct.
AKA 'inattentional blindness'
Inattentional 'blindness' might have been a factor if indeed Oswald was outside (but not noticed) as some here are arguing
The same kind of argument may be applied re inattentional
deafness and the stairs
In any case:
billchapman