By default, some keystrokes that are useful in Vim contradict with the keystrokes of IntelliJ.
For example, ^R
in Vim is 'redo', but in IntelliJ it's the shortcut for Run
To decide which program interprets the keystroke, go to Preferences -> Other Settings -> Vim Emulation
and choose which keystrokes to use with IdeaVim and which to use with IntelliJ: