This poem scans like a national anthem: short, snappy lines, easy-to-remember refrains, and larger-than-life images that transform an entire continent into a gorgeous woman.
Think about it: the first stanza reads like a love poem. The admiring speaker sketches his (or her) love – the woman-continent – and it's pretty clear that she's the bee's knees. In fact, she's so amazing that we're sold on her by the end of eight lines.
Which is precisely why we care so much about her sorrows and suffering. (It's like the part in "The Star-Spangled Banner" when the rockets are glares and the bombs are bursting.) We care because we're already in love.
Come to think of it, the rousing finish in Stanza 3 is pretty much that part when fireworks start going off and we all tear up because "the flag was still there." The image of Africa striding is just the sort of image of a strong, enduring figure that almost every national anthem features in some way. You can almost hear the drum roll and the soaring applause, can't you?