system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why General Petraeus needs to resign over this affair?

Cheating can cause problems for elected officials due to their allegiance to their constituencies, however I am at a loss as to why an individual of General Petraeus' skillset, history, and critical engagement in warfare strategy would be subject to this scrutiny.  He is not elected and does not answer to the public.  Why did he have to resign?
gpt
A large reason is because the CIA doesn't want its top executive to have been black-mailed should it ever come to that over this affair.  It's almost standard practice.

Also, he was pressured to resign by the FBI, who were the initial group to find out about the affair in the first place.