"Dulce et decorum est pro patria mori." (Horace)
"Monumentality" comes from the Latin verb: monere: "to remind" -- but also to warn.
The monumental monument supposedly reminds us of what it is dedicated to. Examples: The National World War II Memorial (here) is supposed to remind us of the Americans who fought, suffered and died in World War II. The Lincoln Memorial (right) is supposed to remind us of Abraham Lincoln.
But change the dedication and the monumental monument could be "about" just about any "big event". It is like an abstract picture that you don't know what it's about unless you read the title.
What does the monumental monument remind us of, if we just look at what it is?
The monument's monumentality reminds us of Power: The Power that could command the building of such a big ("imposing" [on us..]) edifice.
The dedication directs us to imagine instead that all that Power belongs to what/whom the monumental monument is dedicated to.
The dedication encourages us to imagine we can be "powerful" by participating in Power → by obeying it just like those to whom the monument is dedicated obeyed (and suffered and died...) before us. Projective identification.
The power to obey is only the "power" to suffer.
The monumental monument "inspires" us into wanting to suffer for Power.
If we identify with the "symbolism", we feel "uplifted"; if we look at what the monumental monument itself tells us, we feel intimidated, since the same Power that raised such an impressive building can come down on us, and we feel small also because (obviously) the building itself is much bigger than we are.
Therefore the the builders of a monumental monument needs to dedicate it → dedicate it to anything but what it is really dedicated to: imposing on ("inspiring") us to want to subject ourselves to and suffer for the even further empowerment of their Power over us.
"It's not a civilized situation; it's a heroic one." (Vincent Scully; quote out of context)
It's a bit of a stretch rhetorically, but politco-economically incisive to say the goal of monument-ality on the part of the governors is to produce monu-mentality on the part of the governed.