Seems kinda sad to say so, but the answer is pretty evident, I think. Were we to ask a roomful of young adults in America, right now, "who is the current Secretary of Defense?" .... I'm sure that a few hands would pop up, but a startling amount of hands would not. Were we to ask that SAME group "Who is Justin Timberlake?" I dare to predict not a hand would stay down. It's all about 'visibility', I think ... not so terribly much about 'importance'.
But, I will offer this, too: comparing Robert McNamara to Michael Jackson is about as apples vs. oranges as I can think of

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