For social animals (humans included) behaving morally can be adaptive behaviour. Your fitness is increased by group fitness.
Notably, present human society has allowed tremendously unethical leaders to rise to the top of given nations and organizations despite the average person usually having basic ethics.
Animals, humans included, don't really have "morals" - they have survival instincts that result in behavior that may be viewed as moral, but whose origin is indeed survival of the fittest and millions of years of co-evolution.
e.g. Males don't typically fight to the death over territory or females, but this isn't because they have some morality code over unnecessary death - it's because death-match fighting endangers themself just as much as the other guy, and so evolution has selected against that level of uncontrolled aggression.
Evolution is also (really primarily) selecting for things that help the survival of the species, not the individual, and much of what you may think of as "morality" comes from that - avoidance of behavior that is detrimental to the social group/species, not just the individual.
What's training and all that RLHF stuff?
In any case, these companies are well aware that agents are cheating, and don't need user feedback to discover that or realize that people don't like it. I weakly assume that they are trying to get the models not to cheat on assigned tasks, but this "reward hacking" pretty much goes with the territory of RL - not much you can do about it other than try to design non-hackable rewards.
A starting source- https://pmc.ncbi.nlm.nih.gov/articles/PMC6404642/