Was it ever explained in a comic or a book why Pike wanted to become a slave trader?
The very point of that illusion - made explicitly by Vina as she "introduces" it - was to encourage Pike to indulge in fantasies of a kind that he'd never
act out in real life because of his internalized moral constraints. He never would choose to be a slave trader, but people fantasize
all kinds of things - including, not infrequently, murder.
Leonard Nimoy once made the point that "The Cage" is actually about the Talosians trying to discover what will turn Pike on sexually so that he'll be driven to mate with Vina. When Pike notes that the Keeper can't use his mental powers to implant irresistable hunger, it's the writer's way of obliquely explaining that the Keeper can't just make Pike too horny to resist the blonde, either.
Danger Ace wrote:
An interesting thing to ponder is what would have been Star Trek's fortunes had Jeff Hunter had gone to series? Hunter passed away May of '69 (at age 42) due to complications from a fall and a stroke.
Keep up - this was discussed a couple of pages back. Hunter's problems were the result of an injury suffered during a film shoot that he likely wouldn't have been on if he'd been doing a TV series in California at that time.