Really is sad when you think about it. Extreme as their actions were, the Primordial Gods took zero pleasure in this bloody, dirty business. They truly believed that they were doing the right thing, and held to their convictions to such an extent that, once they were certain there were no other loose ends, they offed themselves to take the secret with them.
Both sides genuinely thought they were doing the right thing. That their method was best for protecting their descendants and the world at large. But their methods ran too counter to one another and left no room for compromise.
Personally, the saddest part is that on top of that, their actions in trying to hide everything away so fully are what made the worst result come true in the end. Which, hardly surprising, but still sad, especially since they can't even try to fix on account of sacrificing themselves to the last.
Though, even as I say that, it feels like a set up for a deus ex machina moment.
Both sides had their own pros and cons.
By leaving a record of the event, in case the worst-case scenario happens, the world can fight with the knowledge of what it will be facing.
Yet leaving a record also means leaving dangerous knowledge, like how to undo the seal, to fall into the wrong hands, like what happened in this chapter.
On the other hand, by erasing any records of it, the primordial gods can prevent any information and knowledge from falling into the wrong hands.
Yet this series of events itself proves that when the worst-case scenario happens, most gods won't know the eventual destruction that will fall upon them.
The current event is when both worst-case scenarios happen. The knowledge falls into the wrong person, and most gods are none the wiser.
For my part, I think leaving a record is the best way. Even when the primordial gods erase all information and knowledge of the events, they can't erase the fact that the seal exists. With enough time, someone will find the seal's existence. They don't know what it is, but the knowledge that there's something there will make the more curious gods try to uncover it. Will the gods find the truth before opening the seal and try to hide it, or will they open the seal without knowing what is inside? Either way, there will be another conflict.