I don't know if CMBB has any less "mass appeal" than CMBO. It has even more "eye-candy", the graphics and sounds are both better. Just watching the movies is fun.
In addition, users can make themselves more "powerful" versus the computer in the handicap system, etc., if they want an easier time of it.
Ultimately, what do you think the difference in "less gamey/more realist" between CMBB and CMBO is, in percentage terms? Maybe 20%? That's not a real huge hump to get over, particularly for those who bought the first game, and even for new players who may be interested in this kind of game. Certainly, I've never really played an infantry tactical simulator before(I've done only tanks), but I haven't had any issue with the "realism" issue.