And the same thing would apply to with Satan. According to this article: Our Readers Ask . . . Did God Create the Devil?
How, though, could a perfect spirit creature—who had neither weaknesses from within nor wicked influences from without—become wrongly inclined? He evidently craved worship that belonged only to God and saw the possibility of bringing humans under his rule instead of that of Jehovah. By continuing to dwell on this prospect of rulership instead of dismissing it, he allowed the idea to fester until, at last, he acted upon it. The process is described in the book of James: “Each one is tried by being drawn out and enticed by his own desire. Then the desire, when it has become fertile, gives birth to sin.”—James 1:14, 15; 1 Timothy 3:6.
To illustrate: Imagine an accountant who sees an opportunity to manipulate records in such a way as to steal from his company for personal profit. He might quickly dismiss that wrong thought. If, instead, he dwells on this possibility, then the idea will grow in its appeal, and he is likely to carry it out. If he does, he has, in effect, made himself a thief. If he lies about his crime, he becomes a liar too. In a similar way, by cultivating wrong desires and acting on them, the angel whom God created used his free will to engage in deception and rebel against his Father, thus making himself Satan the Devil.
But I think that the Watchtower is shooting itself in its own foot with these 'imperfect humans' illustrations because why would a perfect spirit creature even 'see' or imagine a selfish and hurtful opportunity or possibility? Because even as an imperfect human, I read or watch videos about corrupt and hurtful behavior by people just about everyday in the news. And I would say that just about everything that I read or hear about, usually has never crossed my mind as an opportunity or possibility. Therefore, why should it cross the mind of an entity that was created as good and as perfect as God could have made him? However, according to Watchtower reasoning, Satan's sin was inevitable too.