Most of the Fallout 1&2 fans and the Wasteland fans are the ones who funded it. And yes the PC market is more receptive, but most of the people that would buy it have already through kickstarter.
One problematic assumption here is that all of those fans have
heard of this Kickstarter project. While news obviously spread fast underground for something with no commercials or ads to do so well, it's a considerable leap to say it reached everyone on the internet. I had personally never heard of Kickstarter until everyone was talking about Tim Schafer using it, and I don't go to a lot of gaming-oriented sites; if I hadn't seen this forum talking about it I may have never found out about the project at all. Ironically, part of why I don't visit those sites is because I'm more interested in those older games that don't get made anymore, and don't care much about the industry today. Plus, not all of those people who were fans and found out about the project may be willing to donate. It's an untested method and people aren't always willing to spend money on something without having a clue what they're getting, not to mention not getting it anytime soon.
Fallout 1 and 2 both sold well over 100,000 copies. This was over ten years ago, when the market was
much smaller. Even if only the fans of Wasteland and Fallout 1/2 buy, they can easily get more than double the copies sold than the number of people who donated. Terraria, an indie game without the advantage of a known predecessor/designer, and with scarcely any advertising, ended up selling...well I don't know how many eventually, but I do know more than 500k copies. Turn-based isn't even that much of a niche, considering that phrase applies to almost the entire JRPG market, including Final Fantasy and the millions of copies it sells. Quite a different type of game, but still turn-based. Honestly, even if the game
isn't good it won't surprise me if it sells more copies than the number of people who donated.