Except that according to the episode, it wasn't a possession, but a malfunction. In Spock's words: "Apparently, subatomic particles from that field have invaded our computer's circuits, much like bacteria infect living matter. As a result, the Enterprise is suffering the electronic equivalent of a nervous breakdown."
Sure, you could surmise that Spock was wrong and it was an alien entity possessing the thing -- but the catch is that Kirk wouldn't have known that
. He would've been acting on Spock's theory, because, come on, it's Spock. So if he believed the malfunctions were caused by contamination from the cloud, then he would've expected a second cloud passage to worsen the problem, not solve it. So what would've been his motivation for tricking the computer into going back to the cloud?
And that's another thing. It was the computer, not anyone in the crew, that set the ship back on course for the cloud. If there'd been some entity caught up in the computer that just wanted to get home, it would've done that right off the bat instead of days later, and it wouldn't have needed Kirk to goad it into doing so. The computer thought it was playing a nasty practical joke on Kirk, taking him to the one place he claimed he was terrified to go (which was, of course, Kirk playing a joke on it). And that means that the computer didn't know
that returning to the cloud would have any effect on it. I don't see a way to reconcile that with the alien-possession theory.
And that's even though I wish I could. It would help make sense of the whole stupid situation. I mean, to be capable of humor and pranks and deception, the computer would have to be sentient and emotionally aware -- able to understand and anticipate emotional responses, able to extrapolate and predict other beings' perceptions as distinct from its own, etc. That's far beyond the capability of 23rd-century or even 24th-century Starfleet computers. Heck, even Data couldn't handle something as psychologically and socially complex as humor. So it would make much more sense if the computer had been possessed by some alien prankster entity. But that just isn't consistent with the way the story plays out, and it wouldn't make sense of Kirk's decision even if it were true. Sorry.