Maybe it's because Lewis has no problem juxtaposing the likes of John Milton with Beatrix Potter. I find enchanting the following paragraphs from Alan Jacobs' The Narnian: The Life and Imagination of C.S. Lewis:
You can see Lewis's love of children's stories in the oddest places and in the most charming ways. In one of his most learned and scholarly books, A Preface to "Paradise Lost" -- and "Paradise Lost" is as sober and serious and adult a poem as one could imagine -- Lewis quotes his eighteenth-century predecessor at Magdalen College, Joseph Addison: 'The great moral which reigns in Milton is the most universal and most useful that can be imagined, that Obedience to the will of God makes men happy and that Disobedience makes them miserable."
A few sentences later Lewis responds to a fellow literary critic, E. M. W. Tillyard, saying:
"It is, after all, the commonest of themes; even Peter Rabbit came to grief because he would go into Mr. McGregor's garden."
To which Alan Jacobs comments:
This is as delightful as it is wise: any literary critic who can, in the course of a few sentences, take us from the great Milton's account of the Fall of Humanity, in twelve books of stately and heroic blank verse, to Beatrix Potter's rather humbler account of Peter Rabbit's rather humbler troubles, is a critic of (to put it mildly) considerable range. And the naturalness with which he achieves this! -- clearly it never occurs
to Lewis to imagine that there is some great disjunct between Milton's world and Beatrix Potter's, and once he puts the likeness before us it's easy for us to see too. After all, leaving aside the one fact that Adam and Eve's decision was disastrous for all of us, while Peter's was (nearly) disastrous just for himself, the two stories have a great deal in common. But it takes someone of Lewis's peculiar stamp to recognize (and more, to declare, in a public, academic setting) the ethical shape of a narrative world in which obedience to Just Authority brings happiness and security, while neglect of that same Authority brings danger and misery. Few writers other than Lewis could open to us that sphere of experience in which John Milton and Beatrix Potter can be seen as laborers in the same vineyard--- that sphere in which a moral unity suddenly seems far more important than those otherwise dramatic differences in time, genre, and purpose."