The protagonist is the guy we're supposed to care most about. And who could we care more about than Pierre, the bumbling seeker of wisdom who wanders the book in search of answers about the meaning of life? Go, buddy, go!
Pierre has his counterpart in Natasha. Not that she's trying to find the meaning of life, so much – but you could say that she's trying to find the meaning of love, or least to figure out how to have an adult relationship. It's fitting that just as Pierre figures out what the point of life is, the two of them find each other and start a good life together.