Normally you don't bother marketing to non comic book readers. But in specific instances where you have creative teams who have fan bases outside comic readers, then it becomes a possibiity. ie if a person who doesn't read comics likes Coates work, you market to them in hopes they will read a comic Coates as written. That's the upside of occasionally getting a writer outside comics to come in and do stuff. Because otherwise, marketing a comic book to a non comic reader probably won't be all that effective.
But yes... odds are good if a book is relying on non comic book readers to survive it won't survive. That said, if you see some degree of sucess in trades and such, it's possible that character can get a second win. This system won't necessarily save a book the first time around (though it has happened if a book manages to at least survive long enough), but it can potentially give a book a second shot.