Someone probably has said this already (and I'm not going back to see if one of you did like five years ago
), but Tom is JRRT himself naturally...
And I mean it. It's the obvious solution.
Or then like a Finnish comparative-religion academic said in a radio-programme this summer; he's an offspring of an earlier Tolkien story he had gotten so fond of that he just wished to fit him in in the early stages and never got to write him out later as he didn't actually fit in... and most of you guys probably can give a list of letters of the Prof. to either comfirm that or to rebuke it.
I like my theory the better but the latter seems quite credible.