Politico.Eu underlines the conventional aspect of a “Jupiterian Presidency”:
The Jupiter theory contends that the president is the supreme authority. He cannot be a micro-manager. The cabinet, under the prime minister, must deal with daily politics. To the president the long-term thinking, as well as domestic and diplomatic strategy. His authority depends on the scarcity of his words. And everyone, from the PM on down to the presidential party’s MPs, must just work toward implementing the presidential platform.
That sounds reasonable, if not the definition of being micro-managerial…
Reuters has a different theory, that the concept doesn’t relate to a President ruling through his cabinet, but rather through the President being dignified and deified as a Roman God – a man who can do no wrong:
These are nice, and diplomatically workable, theories – if you only mean to talk geopolitics…
Many of the ruling class, politicians and nobility, are educated at private boarding schools. They come from a different class, with the power, money, and connections to succeed where others cannot. If they don’t make a career in the public sector, they make one in the private sector, replete with all the connections the schools can provide.
So in this context, what can be derived from his comment?
It’s an inside joke for his boarding school buddies.
Other than the blatant pagan worship, Ancient Roman traditions declare that Jupiter cannot exist without Janus… Jupiter is first in order of importance, sure, but second to Janus in order of time.
Macron was therefore making a very archaic reference, essentially calling himself the Janus AND the Jupiter, “Alpha and the Omega, the Beginning and the End”. He was hinting in an egotistical belief of being God Incarnate (Revelation 22:13).
While this does sound really weird, the elite tend to go to private boarding schools, where they learn about the Ancient World and its impact on our Modern One, which is why Boris Johnson is fluent in Latin.
Tl;DR: Macron is literally a Janus; a two-faced politician.