Alternatively, you could look at it as if God is actually a kind and gentle god as so many christians say he is, would not living a good life helping others and being a good person be enough to earn his favor? Or would a person who poisons and kills hundreds of people by contaminating a town's water supply on purpose with a disease/virus that slowly kills someone, yet later in the last few years of his life says "wait, nvrmind. My bad." and converts after killing hundreds of people and living a life of absolute sin get in because he believes in god and asked for his forgiveness? If the first one goes to hell just for not believing, then I'll be with a bunch of other nice atheists burning in hell.
Aside from the obvious religious significance given the dominant religions of the time in the areas these monuments were built, and the fact that a lot of religion used astrology and these monuments point to certain major star on major days of the year (summer/winter solstice, spring/fall equniox)?
Hiding alien spacecraft? Most likely not. Hiding the crashes/ sightings of tp secret military aircraft? You bet.
Given that a lot of UFO sightings in the 80's were of a triangular shaped craft that seemed to zoom around at high speed, yet civilian radar never picked up anything in the area around the time of the sightings, and then this got declassified in 1988 from being top secret: