It's impossible to overstate the good that Mr Nelson did with TAN Books. Just speaking from my own experience, TAN provided a way to get books that weren't available at the parish level, and those magnificent green catalogs were virtually a catechism in themselves, of what the Faith was like before the Vatican II era, something that the change agents at the parish level were hoping everyone would just forget (or if you were young enough, never be exposed to in the first place). As I understand it, TAN also did secular publishing to subsidize the books that would otherwise not have been commercially viable, and use of a nondescript corporate name (Mr Nelson's initials) made this easier, not to mention that there was already a Thomas Nelson Publishers, a Protestant entity in Nashville.
Requiescat in pace.