Consider the Lean Startup methodology. The darker patterns are where you break down the big picture rationale for the company. You extract metrics that contribute to the company's success (i.e. engagement) and you build a machine that rewards changes to the underlying system that improves those metrics.

If done successfully, you create an unwitting sociopathy, a process that demands the product be as addictive as possible and a culture that is in thrall to the machine that rewards its employees by increasing those metrics. You're no longer thinking about purpose or wondering about what you're doing to your users. You simply realise that if you send this notification at this time, with this colour button, in this place, with this tagline then the machine likes it. Multiple people might contribute a tiny piece of a horrifying and manipulative whole and never quite realise the true horror of the monster they've helped build.