The sum total of FS2's advertising campaign was a two-page spread, in a few print gaming magazines, that ran for two months, and the trailer was included on the CD for
Descent 3. On the subject of D3, Interplay, at the time of D3 and FS2's release, had a bad habit of not just under-advertising their games, but also focusing their advertising on groups who were already likely to purchase the game in question. The main thrust of
Descent 3's advertising campaign were two $50,000 tournaments, which chiefly appealed to people who were already high-level Descent players, not fresh-faced newbies, leary about the whole "six degrees of freedom" thing.
To your other concerns, though, you raise a good point about mandatory hardware 3D acceleration. 3D accelerators were by no means obscure at the time, but they had only just been worming their way into the minimum requirements for games in 1999, and it did put off a small number of people, who had felt that their computers would be able to manage as gaming machines a while longer, without an expensive video card. I doubt that removing this requirement would have launched FS2 from the status of 'commercial flop' to 'megahit' or even 'modest success,' but at the time, it certainly would have had
some kind of effect on sales.
I think FS2 died based on obscurity and not being able to be put it front of multiple gamer audiences (console + PC).
I mean no offense, but I think you betray your age here. Consider the big three consoles of the era: Dreamcast, Playstation (1), and the Nintendo 64. FreeSpace and FS2 would have had to have been made into much,
much different games in order to run on any of these consoles, due to the extreme limitations presented by the hardware, nevermind the controlers. This was a day when consoles ran with processors at a sixth the clock speed of their PC counterparts, and even stripping out the unrelated background processes that most PC games had to compete with for CPU time, the consoles just could not keep pace. PC ports of console games were generally panned for looking hideous and being tremendously unstable, while PC games could rarely be ported to consoles at all. Had either of the FS games been pared down to something that could be handled by a console of its era, I doubt that it would have formed such a dedicated following.
