Nobody accomplishes anything of note without the inputs of other people...all of whom are similarly acting out of their own interest.
Collectivists often point to this as an argument in favor of their worldview....basically that the individualist worldview is one which sees man as Robinson Crusoe, doing everything by himself and for himself.
This is completely wrong.
This became a matter of substantive debate back in the Obama years when he made his comment about "you didn't build that!" He actually lifted that line from Elizabeth Warren, as I recall. They were referring to public infrastructure. But they were also noting that successful entrepreneurs rely on the labors and inputs of others (employees, suppliers, contractors, creditors, insurers, etc.).
So where's the disconnect?
Well, it's that everybody does most of what they do out of self-interest. Adam Smith captured this perfectly in Wealth of Nations:
“It is not from the benevolence of the butcher, the brewer, or the baker that we expect our dinner, but from their regard to their own self-interest. We address ourselves not to their humanity but to their self-love, and never talk to them of our own necessities, but of their advantages.”
Collectivism and altruism are ideas that center around the concept that we should do what we do in the interest of the collective or of others...that our self-interest should come second, at best.
The reason this doesn't work is that it defies human nature.