Football didn't dethrone baseball. Popular as it is, football has nowhere near the cultural status that baseball once did. That's not because baseball declined -- it's because the American public's relationship to sports did.
Baseball was a cultural institution; football is guys yelling, "WOOOO?!" at their televisions for twelve hours at a go.
There's no film famous for the line, "If you strap on a mattress and bash head-on into a roided-up bovid like you, they will come."
Kids don't collect football cards, if there even is any such thing.
Baseball stopped being the national pastime not because baseball died, but because having a national pastime did.