How does the gospel of wealth justify the philosophy of social darwinism

The central idea behind Carnegie's essay was to illustrate the hazards of allowing large sums of money to be passed into the hands of persons or organizations ill-equipped mentally or emotionally to cope with them. As a result, the wealthy entrepreneur must assume the responsibility of distributing his fortune in a way that it will be put to good use, and not wasted on frivolous expenditure.

In other words, only the most successful and mentally capable members of society should have the power of deciding how capital wealth should be spent to alleviate society's problems (poverty, diease, hunger, etc). Such an idea is very compatible with Social Darwinism, which favors the strong and rich over the rest of society.