How is it that people working in their own self-interest produce goods, services, and wealth for others?

In order to earn money and produce goods that improve lives, self-directed gain would provide jobs, and subsequently wages for others.

The way people can become wealthy by their own efforts is to sell what they produce to others. As the business grows, labor is hired to produce more. This is the 'invisible hand' concept that turns self-directed gain into social and economic benefits for all.