Because man created God in his own image, and then wrote stories about God in which he returned the favor.
Some jealous, wrathful men created one image of their god. But not all fall in this category.
BG Ch 2
60 Turbulent by nature, the sense even of a wise man, who is practicing self-control, forcibly carry away his mind, Arjuna.
61 Therefore, having controlled them all and collecting his mind, one should sit for meditation, devoting oneself heart and soul to Me. For he whose senses are mastered, his mind has become stable.
This god sure is stable minded.
Still further.
62 The man dwelling on sense-objects develops attachment for them; from attachment springs up desire, and from desire (unfulfilled) ensues anger.
63 From anger arises infatuation; from infatuation, confusion of memory; from confusion of memory, loss of reason; and from loss of reason one goes to complete ruin.
This god can be a slave of anger, jealousy etc, can he? Witness. Ch 14
22 He, who is contented with whatever is got unsought, is free from jealousy and has transcended all pairs of opposites (like joy and grief), and is balanced in success and failure, -- such a Karmayogi, though acting, is not bound.
Why would a god need motivation?
Why, indeed.
Moreover, Krishna is not driven by some selfish motive. Witness. Ch 11
22 Arjuna, there is nothing in the three worlds for Me to do, nor is there anything worth unattained by e; yet I continue to work.
23 Should I not engage in action, unwearied, at any time, great harm will come to the world; for, Arjuna, men follow My path in all matters.
24 If I do not perform action, these worlds will perish; nay, I should be the author of confusion of castes and the destruction of these people.