It's because billionaires are planning on living forever.
When you are going to live forever you won't be able to keep it a secret.
Controlling 10 billion people is much different than trying to control 30 billion.
When illness and death is no longer a concern for you, your only concern will be dying at the hands of another person.
Forever is a long time.
They want the whole planet.
Its easy to be successful. Under a fair gov't that assists its citizens, we would all be upper middle class. Houses would be subsidized, markets would work for the people, not the elites.
Problem: too many people wanting too much. So the ELITES who have gotten their share of the wealth obviously see it being consumed by new arrivals. Soon they argue, we'll all have just our own slice, with everyone fighting over leftovers.
They will in addition to depopulation, shut down most avenues of wealth creation , like small business, restaurants, real estate renting from individuals, and alternative currencies like gold and crypto.