Explaining EJO's popularity

I think there's a thesis in there somewhere. Monica Godfrey's biography which was published a few years ago might shed some light but I have to confess I've only read the intro and looked at the illustrations. In the intro she suggests EJO's enduring popularity relates to the connectedness of her stories, even the ones that are not strictly part of the Abbey series but still have some connection with them thus forming what she calls a "complicated canvas".