It only surveyed people who don’t have children. Says on the left ‘Do not have children, n = 1300’. This result says nothing about the general intention to have children as those with children in each age group are excluded. Naturally, as people age, the number who still think they’re going to have children goes down.
The article says he was collecting weapons for a zombie apocalypse, in this case crazy seems the most likely explanation. Pointing this out is not at all the same as saying you must be crazy if you do something violent.