[gry]

FWIW, Ctrl-[ is ESC's equivalent.

Ctrl-C escapes insert mode, and does not check for abbreviations. It has a different behavior.

    <Esc> or CTRL-[ End insert or Replace mode, go back to Normal mode.  Finish
                    abbreviation.
                    Note: If your <Esc> key is hard to hit on your keyboard, train
                    yourself to use CTRL-[.
                    If Esc doesn't work and you are using a Mac, try CTRL-Esc.
                    Or disable Listening under Accessibility preferences.
                                                    i_CTRL-C
    CTRL-C          Quit insert mode, go back to Normal mode.  Do not check for
                    abbreviations.  Does not trigger the InsertLeave autocommand
                    event.

https://vimhelp.appspot.com/insert.txt.html