What could possibly go wrong?

from here and here (image source)

This gentleman is demonstrating something far more elaborate than footguns, but it is essentially the same premise, and also the same premise as disabling your antivirus when installing new software. 

If you want it to be easy malware authors to trick users into lowering their defenses, just normalize the practice of disabling the antivirus when installing software. Once it becomes normal the malware authors can ask users to do the same thing.