They who persecute believing men and believing women and repent not, theirs verily will be the doom of hell, and theirs the doom of burning. 85:10
No one knows who the owned the ditch or why they self-destroyed. It's just another mystery of the Quran.
The Quran asks its readers if they've heard the stories about the Pharaoh and the tribe of Thamud - stories that are repeated told throughout the Quran. So this answer to this question to anyone who has read the Quran is "Yes - way too many times."
