I wouldn't go that far. The number of jailbroken phones was a fraction of a percent of our user count, but 100% of our known cheater count. Every single one.

how was the jailbreak state detected?

A bunch of the filesystem was visible to all apps that isn’t visible on a regular phone. I’m sure someone smart could have gotten around the detection, but nobody cared enough to do so.

As effective as using an atomic bomb to kill flies!