i can't speak to all of the monoliths that have been erected. but this one seems unusual because it was "near Gass Peak in the Desert National Wildlife Refuge" (not a location that is easily accessible by car) and it was "made of folded sheet metal and held together with rebar and concrete, authorities said."
That sounds heavier than one or two people could just carry on their own, but maybe I'm overestimating that.
One was right at the end of a car road. Another, it says 4 people were needed to dismantle it. But even for the more inaccessible places, there is also helicopters.
Why? One is a physical art installation and the other is an internet based puzzle. Doesn't seem to be any kind of connection other than being mysterious. Not saying it is impossible, but seems unlikely