Behind the monument is the celebrated ruin of a society that overspent its way into its collapse, and chiseled for itself its own tombstone. It justified to itself the need of a great public works project, or took a legend too seriously, or felt strongly about a war it dragged itself into; money was created, currency was issued, and jobs were promised, and there was a brief time of prosperity.
There is no other known way to express the elation of being at the top while leaving behind a reminder for whichever peoples that may come after. The monument made at leisure, in prosperity, but always with the approval and oversight of the authority. These are not visions of an artist created in a state of inspiration; these are bureaucratic decisions, signed off or stamped on by some power-structure. Think of when you or someone you know ever asked for a monument – who ever does – the request and the decision on that request always comes from the top. If, say, a personal creative endeavor does acquire enough importance for a society, it becomes a shrine and the authority lets it stay as long as it doesn’t pose an ideological threat to it. And later, maybe, it can have a chance at becoming a monument.
The monuments might reflect the manufactured-zeitgeist, or be an imposition by the ruling elite upon its subjects – whichever way, these are points of time in a society when reminders become necessary. Under these reminders is a fear, of the inevitable fall, because that is the only way ahead from the top. There is the fear of decadence; of bankruptcy, both moral and financial.