Because the 'who' was the 'president.' Where the buck stops. The committee's failure to hold the Executive responsible can only be rationalized through the nebulous doctrine of Executive Privilege.
When or if this history is ever properly written, perhaps after we are all dead, it will be seen clearly that this 'president's' oaths were a lie and he lacked a conscience.
"Murder, though it hath no tongue, hath by marvelous means out."
Well, either that, or a huge load of chicken chittery.