Either because that came upon them unexpectedly, which they looked for indeed, but supposed more distant; or because they thought their perdition consisted in this, that when known they would be despised; or because this was before the day of judgment, when they should be punished with eternal damnation.
Reproduced in full. Translation: Oxford 1841 (Newman), public domain (Public domain).
Also cites: City of God, book 8, ch. 23