I doubt they're claiming to have anything novel in their heads. It is like WWII where the militarily engaged people probably had a pretty good idea of what was about to happen as Europe descended into war. The citizens didn't really understand and there wasn't the level of diplomacy and panic in the early stages that the eventual crisis would have justified.
If the average citizen had a good understanding of what an industrial war looked like and what was possible, they'd (taking an optimistically charitable view) have spent the 20s and 30s being a lot more vigorous in trying to keep the peace. Like the efforts we say from the 40s to around the 2010s where people who remembered WWII put huge amounts of effort into not letting it happen again.
