That's only part of the truth. Animals do cooperate within and even across species, but they also compete, even within a species - wolves, ants, and chimpanzees are all territorial (as are many others), and the latter two are known to engage in war within their own species: https://www.livescience.com/animals/land-mammals/a-decade-lo...
And the competing against nature itself you mention, is often determined by the territory a group is able to claim. Some places get drought, others freeze, and in others food is plentiful. Nature may not be a free-for-all deathmatch, but it's not a pacifist coop either. At least, most species don't behave that way.
Oh certainly. But that's the thing. Even with species being territorial, that serves a broader purpose in the ecosystem. Territoriality for predators is important to prevent concentration of predators, overpredation, and then depletion of prey species (which has many downstream effects).
And because of that, territoriality tends to be fairly low in most species until the food supply becomes constrained. And even then it's a gradient where hostilities generally only escalate out of desperation rather than innate competition. i.e. Competing between individuals or communities tends to occur mainly when they fail to compete against the environment and run out of other options.
But really my point was just about the general sentiment that it's "against evolution" or "against natural selection" to help the weak and that doing so is something that humans do out of a unique sense of love or kindness or whatever.
And the competing against nature itself you mention, is often determined by the territory a group is able to claim. Some places get drought, others freeze, and in others food is plentiful. Nature may not be a free-for-all deathmatch, but it's not a pacifist coop either. At least, most species don't behave that way.