the Golden Path is the survival and continuation of the human race. no more, no less.
to achieve that end, Leto II consolidated the known universe under his rule and enforced millennia of political/cultural/economic stability and tranquility. the whole point of this was to build up wanderlust, innovation, and rebellion against charismatic authority
by concentrating power in his hands, that meant that his death would be the bursting of a societal dam that had stood for millennia, releasing a torrent of energy and expansion which became The Scattering. by spreading the human race far and wide in the universe, by breeding prescience-cloaking genes, by encouraging innovation (no-globes, ixian navigators, etc.), and by weaning the human race off of their dependence on spice from Arrakis, he ensured human survival.
he didn't do this for power, narcissism, or long life. in fact, Leto II took on a huge burden and sacrifice (which was too much for Paul-Muad'dib) to prevent human extinction.