Why would any Alien Group need to make on the surface of the spinning Earth Cosmologically minuscule stone Megastructures in the rough shape of their star system?

They have already gotten to Earth without them being in place, and already know exactly where Earth is. They do not need flat stone surfaces to land or launch their craft. They do not need the energy from an Earth sized power grid, because they already have immense power. They need no transmitted information from Earthlings sent to them via a pyramidal power grid, because they already have AI or its equivalent.

There is no rational reason for mapping out time durable Alien star clusters with extremely high tech stone Megastructures. No reason at all.

Having them be a record of past Alien presence makes no sense, since the megastructures have no imprinted information or narratives upon them, other than a few indiscipherable symbols.

Nobody here is bright enough other than me to even frame this perspective and question, let alone answer it. Why is that? Are you people in a fog?