Why not work for charitable causes directly?

His multiplier effect was higher by making tons of money and then giving it away, rather than working for charitable causes directly.

For example, take two simplified cases:

1. He makes a lot of money, and as a direct result of his fortune and generosity, he can effect [1000 employees * 10 years] = 10,000 man-years of charity work

2. He works directly at a charitable institution and performs 30 direct man-years of charity work, but makes no appreciable amount of money to multiply his efforts

If you're interested in a better explanation of this with regard to charity, I would check out Singer's book "The Most Good You Can Do", which is an exploration on the theory of effective altruism.

Plus anyone making money is contributing to their work. A doctor saves lives in exchange for money. An entrepreneur solves small problems that thousands of individuals face.

Division of Labour.

That's like saying "If you work to buy a house and food, why don't just build it instead along with a garden in the back and not work?" To which the answer is it is cheaper to do what you are best at and sell the surplus to buy all the houses your new money can afford.

I think I know what you are trying to say, but you are describing the idea of "competitive advantage" here.

You are correct, what I describe is "Comparative Advantage" not Division of Labour, although I would say CA is a result of a DL at a macro level.

How likely is that to do $8B worth of good for the charity?

Alright thank you, I'll give it a look.