if morality is never involved in a strategy to survive... why do you think it exists?
Then you might wonder, "why does/doesn't every member of the species have that variation?". A suitable answer as I have come to understand is, it depends on whether it is evolutionary stable for every one to have the variation or not have it. Plus you can expect some error margins.
For example, while every one can farm, every one can't be pillaging, a society of all pillagers cannot be stable. You can also see that in a society of all farmers, a randomly introduced pillager will have a blast while not necessarily upsetting the balance. But start introducing more pillagers and the stability will break down at some ratio of pillagers to farmers.
Please note that this is not "selecting what is good for the species", that is only a consequence.
Just like how honey bees produce an abundance of honey. The moment you have any kind of abundance, something will be created to take advantage of that abundance. Nature tries everything.
All farmers - Not nihilistic, Not stable
All pillagers - Nihilistic, Not evolutionary stable
Some ratio of pillagers:farmers - Not nihilistic, Evolutionary stable
Where nihilism means that the society is very self defeating that it collapses instantly. And evolutionary stable means that the society can maintain it's general composition for a long enough time period.
P.S: There is probably a better word than nihilism for what I have chosen it to mean.