I think the explanation is simpler than this. In any communal organism, there are two competing evolutionary desires: the desire to beat everyone else around you (and therefore be the fittest and spread your genes the most) and the force of cooperating to build something bigger together (so there's more to go around, so you have more resources with which to spread your genes alongside everyone else.)
Only lifeforms like solitary bacteria have only the first evolutionary desire, and no communalism at all. Any organisms at higher levels of evolution use cooperation.
We can look at a hypothetical wolf pack, for example. Every wolf has thought at some point that, "if I simply killed the other wolves in my pack, I could eat more of the current catch. But if I do that, I won't ever be able to get another big catch again because no one will be left to help me, so I won't."
Imagine instead if this wolf pack killed the weakest member every single time because that's "just wolf nature." Every wolf is weak when they're young, when they're old, or when they get sick. Pretty soon, if you keep culling the weak, there will be no one left in the wolf pack, and it will die out. Therefore, evolution favors some amount of communal benefit.
Human civilization would not exist if we spent all day just competing with each other. If Caveman 1 killed Caveman 2 instead of deciding to all work together on agriculture, all of us would still be living in caves eating rocks, no better than bacteria. Everything great that humans have ever built has been built through working together, not through killing each other to see who is the strongest. Therefore, it makes sense that, while capitalism has done a great job allowing more people to work together on innovations than feudalism, it also makes sense that we should progress to the next stage of cooperation via socialism, so that we can all work together to build a state and industry, and live better lives (and have more offspring if you really want to fulfill your 'human nature' evolutionary desire).