[BOOKS] What did Lukas really learn and say to Bernard?

I was a bit puzzled by how the show managed this bit. It seems like the big "secret" was only about the existence of the safeguard (Silo 1 being able to kill all the other Silos) but that didn't feel like such a strong reason for a lot of the characters' actions.

Lukas already learns about the safeguard from Quinn's message, so why does he seem so shocked only after he speaks with Silo 1, apart from having it confirmed? Is this information really enough to push Meadows to become a recluse alcoholic for 25 years and Bernard to completely check out and basically kill himself? They already knew about Silo 1 having a "control" role, is that really earth-shattering to know that they can/are willing to kill them as well?

I am questioning that because we also know from Wool that the real bit of information Lukas learns that could have that kind of impact is that the Founders created the silos not because they knew about the end of the world, but because they caused it. Lukas (and I guess Meadows) could have learned that in the show while discussing with Donald/Daniel/the door in a similar way off-screen. I believe that could be something that would justify Lukas, Meadows ("what have they done?") and Bernard's reactions in the show. Do you think that could be what Lukas really learned and said to Bernard, and why we didn't let the viewers hear it?

The only counterargument I have is that Bernard only mentions the safeguard as an explanation for his actions to Juliette, and I don't see why he would lie or omit further reasons at that point. But the whole safeguard plot seems really underwhelming to me if that's really all there is to it.