I think this is one of those cases where there's really very little way of knowing what really worked and what didn't. It's like a sports team: you can make ALL the right managerial choices, but still fail due to chance and factors outside your control.
At best there are some reasonably good heuristics.
On the flip side you can hire Michael Jordan and screw everything else up and still win. Then go on to write a business book that’s completely misleading because you never realize that you did only one thing right, and that was enough.
Do you have to have seen a human die to know that a human could die? Surely Cain had seen plenty of animals die. I think you might not be giving Cain enough credit (or maybe too much credit) by assuming he couldn’t have put 2 and 2 together
Craziest thing IMO: It doesn't leave its larval stage, but you can give it the hormones that turn other reptilians into adults - and they work! You'll get a living adult axolotl, a pretty normal looking reptile with just a few minor bugs (IIRC).