Did they leave the industry because they realized their product wasn't providing a positive ROI, or were they fired for pointing that out to other people? I think the former is probably what you mean, I just want to be sure.
You can get firms selling stuff that doesn't work that are "trusted" simply because they've been around for years; there are plenty of distinguished brands selling homeopathic remedies, audiophile speaker cables, timeshares and MLM schemes.