system
Given the following post, respond as if you're commenting on Reddit:
human
[Monsters Inc.] Why was Monsters Inc. under investigation by the CDA?

I assume that the CDA would need a pretty good reason to investigate Monsters Inc.  Not only did they conduct an undercover operation, but the **head of the agency** was installed as the undercover agent.  This would be akin to the head of the SEC (someone fairly well-known) taking a job at JP Morgan Chase.
gpt
Probably the fact that Waternoose, the company's chairman, was working on a plan to kidnap children (who are known to be **highly toxic**) and bring them **into** the world.  
It's the equivalent of the head of an energy company having unprotected radio-active material in his office.