@jaw20 No, what I meant to convey was what I think as the reason Adamant is BROKEN, which in his own words manifests in his actual inability, not just unwillingness, to restart the prayer cycle. The original reason he stopped his prayers was because of his desire to be with the Gems, like you said. However, up until that point in time the prayer system was still functioning the way it was meant to do. It was meant to send ONLY the Lunarians into oblivion, and that was what it was doing until Adamant broke the cycle. If he had restarted the prayer back then, perhaps things would have turned out okay for the Lunarians and the Gems. However, ADAMANT would also have perished at the completion of his duties, so it was ultimately his selfish desire to be with the Gems that caused all the problems. Adamant stopping the original prayer cycle was what had caused the energy to build up so that a prayer now would wipe out all three races. Aechmea knows this explicitly and still wants to go ahead anyway. Adamant is subconsciously aware of it, which is why he is now broken. Instead of not wanting to continue the prayer because he got distracted by the Gems, now he simply can't because there's a mental block built up from his need to protect the Gems. Basically, this was all his own fault for falling into his own desire and inadvertently turning himself into a weapon of total extinction.
As for the Gems' impact on the Lunarians, it's much deeper than you seem to think. The people of the flesh are mortal, so they just live according to what nature gives them. The Lunarians and the Gems are both immortal but represent two opposing approaches to immortality. To the Lunarians, their desire for oblivion comes from their eternal boredom and pain from being perfect immortal souls yet living exactly like the flawed original humans did, constantly looping around repeating their ancient follies. The Gems are different in that, while being equally immortal, they could start anew unburdened by the sins of humanity. They love life and continue to strive to make the best of it, staying eternally positive and beautiful. They can accept the pain and continue to make space for each other in their lives. The Gems were born immortal and knew how to live fulfilling immortal lives. Even the stupid civil war the Gems are having now is predicated on the idea that if Phos' side won by breaking to pieces all the Gems on Earth, ALL the Gems would be restored at the end by the victors, and except for Phos all the Gems from the moon would also be restored by their Earthen brethren if they lost. This is the attitude of immortal beings for whom death is alien and life is the ultimate goal; even war is just a tool for settling differences without cost. Phos just doesn't realize yet (because Aechmea is being a dick) that the Gems would also be wiped out by Adamant's prayer.
When the Gems were transplanted to the moon, they brought with them their eternal optimism and beauty and reinvigorated Lunarian society in ways only they could. They taught the Lunarians how to live as immortals the way they themselves have always lived, and Lunarian society changed dramatically. This is even visible in the aesthetics of their city. The current city looks like the Gems' city on Earth instead of the idealized Buddhist paradise the Lunarians originally had. The surfaces are built in stark angles or curving minimalist arches, representing Lunarian society's adoption of Gem culture. The problem is that the Lunarians themselves haven't figured this out. The idea of seeking oblivion have been so deeply ingrained over the millennia that they just automatically embrace it without asking themselves whether they actually wanted to. That's why there was a sigh of relief when Aechmea marked the false alarm and everyone went straight back to what they were doing before.