Actually, I found some pieces of information that make this theory hilarious.
The hollow moon is a stupid thing that got started because the seismographs of the Apollo missions found that the seismic waves persisted for a long time. One of the scientists said that the moon could "ring like a bell" and some people started idiotic conspiracy theories that it was hollow which is why it was "ringing". The moon is way to dense to be hollow... This theory just a hilarious myth!