I would give the credit to Fangamer, as I've said before. This campaign seems to have been pulled off magnificently, ranging from Sword or Whip drumming up a lot of anticipation even before the KS launched to they way they drummed up even more support via social media bonuses. The backer rewards were just as effective, IMO. Given how much people love David Hayter, Ayami Kojima, and Yoshitaka Amano, having those people on board for goodies probably netted the campaign a few million dollars. I mean, 1000 dollar signed prints from Amano were all sold out *within minutes*! Finally, I suspect a lot of the 'clans' for the backers were very influential. From what I hear, some big shot Youtubers gave this project a shoutout and their devoted fans jumped at the bit to follow them. That probably gave us a few more million dollars as well.
The funding for this project seems quite secure. IGA was originally asking for 4.5M from other investors (the last .5M of the 5M total needed for the game was supposed to have been barely reached by Kickstarter), and after all the KS rewards have been given out, I'd say he'll have an extra 3M (out of 4.5M gained by kickstarter, though the number could be higher) to play around with. So he'll have like 7.5M dollars to make a game that he first thought would cost 5M. He has 150% of the funding he'd thought he'd need! Pretty impressive!