Mages and Divine Beings have never had a relationship of dominance, but one of symbiosis, with mages at most being able to take advantage of a Divine Being's favors. And even that advantage is based on the premise of the Divine Being having been well fed (the Legendary Chefs feeding it around the clock without breaks) and wanting to expand its own boundaries voluntarily.
Yet Diya had been with Ash for so long that if he had a bunch of Legendary Mages as a battery pack, she would have noticed. Since she hadn't, it meant Ash didn't have any power to drive the Divine Being, or if he did, it was as minimal as a drop in the bucket.
Nevertheless, the Divine Being still provided him with services custom-made for him, assembling a team for him every night, preparing the sports car, readying the map—his own parents could not do more. There was only one explanation for this: the Divine Being was wholeheartedly at his service, even exerting itself to gather energy to subsidize his upbringing.