Why was Paul Dirac’s proposal about gravity unnecessary according to Robert Dicke?

In 1937, Paul Dirac proposed that the strength of gravity decreases as the universe ages to explain certain observed coincidences between fundamental physical constants.1

In 1957, Robert Dicke demonstrated that Dirac’s radical proposal was unnecessary by introducing what is now known as the weak anthropic principle. Dicke showed that these numerical coincidences were not evidence of changing physical laws, but were instead a necessary consequence of the fact that humanity exists at a specific time in the universe's history. Specifically, observers can only exist late enough in the life of the universe for carbon to have been synthesized within stars. Therefore, the observed values of the constants are constrained by the requirement that the universe must be old enough to support the evolution of life.1