So he ate his crew and for some reason left only three?? All three had to be insane!
Indeed, we have no reason to think they were any more or less insane than Krall.
Although I doubt the guilt over sucking fellow human(oid)s dry would result in insanity as such. It's just a fight for survival, and we accept whatever we need to accept to keep the fight going (say, killing and eating of animals, or taxation of fellow humans, or nuking of Hiroshima or blowing up the Beslan kids, or whatever).
Jaylah managed to survive on that planet, so she must have been eating something.
Sorry, I didn't mean to cause confusion. Edison wasn't hungry in the physical sense. He "ate" other human(oid)s in order to live forever, by sucking them dry with the help of the Ancient arts. For physical sustenance, he probably ate resequenced hamburgers and tofudebeest like anybody else. And I very much doubt he ever had to resort to gnawing on the thighs of his Astrogator's Mate 2nd Class. (Although rationally thinking, it might make sense not to let those dead carcasses go to complete waste.)
Jaylah didn't go hungry, but she also didn't live forever. She ate, she didn't "eat".
"They left behind sophisticated mining equipment and a drone workforce."
'And rather than fix my ship I eat people's souls instead'...
This tells us more about the timeline. Why would Edison suddenly want to live forever when just plain living should suffice? This would only make sense if he was already hell-bent on revenge upon the UFP, and realized that as a mere human, his chances of achieving revenge or even living long enough to properly plan for it were slim.
We know that by the time of his last log, Edison was both aware of the Ancient tech
and already irrationally blaming the UFP for his woes. So whatever made Edison go crazy happened before that, but quite possibly shortly before. And the two possibilities are "natural" insanity from isolation where nobody challenges the xenophobic views of the crazy old soldier, and "unnatural" insanity from innocently trying out the Ancient tech. I guess a mix of the two is possible, but if Edison hated aliens all along, why did he choose to become one himself? It would be neat to assume that the tech screwed up Edison's mind, this also explaining why only those exploiting the tech became baddies.
Was it evil tech? Or was it intended for good, and the very fact that it forced ultimate tolerance of alienness upon the arch-conservative Edison may have been key to him going mad where the original users would not have?
Timo Saloniemi