The best way the wealthy can benefit a mass of people is by creating employment for them.
A well - off person will always look into new ways of increasing their wealth. The wealthy may consider investing some of their money into a new company or factory. A new factory means new employment and work possibilities for many people in a specific location.
Another way of benefiting a mass of people is donating money to a cause. It might be a new school or hospital ( benefiting a large group of people again), a new bus, or a new library wing.
They can also support medical research which is an excellent way to share their wealth for the benefit of many. If a cure for a particular disease is found, millions of people worldwide can be healthy again.