For me it might have been timing - it wasn't terribly long after I started getting into the music (1989) before I heard about Mosaic (probably print ads in DB, I am guessing, then getting the catalogs) but I am quite certain that it was Michael's essay about Brooks as this forgotten/neglected/talented musician that made me want the Mosaic LP set.
What are your recollections? Were you also deeply intrigued about Tina or did you know him from his sidemen appearances already?
What about other Mosaic sets? Did it just take an intriguing come-on from Michael to make you order (or in my case, request for birthday/Christmas)? Or did you rely on prior knowledge, the mystique that Mosaic built up in their golden years, asking online or real-life friends?
I guess part of this depends on age, if you came to the music later you didn't need the Brooks LP set, and our older members of course were buying BN LPs at $5 when they were fresh in the stores or just off the boat, but I'm curious so ... What do you say?
EDIT TO ADD: Just realized Freddie Redd might be an even better example in terms of Mosaic creating a market. The Mosaic came out four years before any BN album reissues. At the time there were probably some OJCs easily available, and the market primed by older folks who knew his music back then. But he was really an unknown quantity to me that I requested purely off of the Mosaic catalog, I am certain.