I think Artos is buried in the crypt primarily because he slew Raymun Redbeard; killing a King-beyond-the-Wall and ending a wildling invasion practically single-handedly is a huge deal in a warrior culture.
Also, it’s possible that, since Willam died unexpectedly, Edwyle might not have been of age to rule when he became Lord, so Artos might have spent some years as Regent of Winterfell.