As someone previously mentioned, if you get someone at HW with the mystique of Mike Tyson, in all likely hood they'd outdraw everyone else. Like you said though, there is still room for the smaller guys to be popular, under the current system the odds of that aren't pretty, but they exist.
Light figters are less marketable the HWs, and thats the point of the subject.
I did not say they are not marketable at all.
In fact, when you look at weight divisions, as you go up, fighters became more and more marketable