iTerm2 > Preferences > Advanced
Mouse > Scroll wheel sends arrow keys in alternate screen mode.
Easy access from the search window with scroll .
Scroll wheel sends arrow keys in alternate screen mode. setting changes the scrolling behavior as follows.
Yes : Scroll in the Vim window
No : iTerm window scrolls regardless of Vim
In my case, since there are many cases I want to paste from Vim in past console logs, I set the setting to No so that the iTerm window scrolls.