Please note that Ctrl-C does not do the same thing as Esc or Ctrl-[.
More info: https://unix.stackexchange.com/questions/53633/does-using-ct...
Well, it's the same if neither you nor a plugin uses abbreviations nor InsertLeave.
Also, if you don't need that particular behavior of <C-c>, you can do `:map <C-c> <Esc>` to make it behave exactly the same.