and then dmd made tons of money.You DO realize that DmD or BB were not the first (nor will they be the last) games with this subject matter? The genre and ideas have been around for thousands of years, and yes even months/years before either of these games were even thouight of.
seriously, you can have that idea around even for hundred of years. if it's worth shit, nobody will try to copy it. when it makes lot of money, instead, everyone think they can do it too and make money.