Good question. It's mostly about momentum. Let me give some more detail on the development history:
2012: I did a bunch of work for 6 months, released an Alpha, got all excited with the feedback. Then I spent another 9 months on it evenings and weekends.
2013: I was concerned for the market for the game then Star Citizen and then Elite: Dangerous were announced. I stopped for 6 months and did a web based prototype of the history code to check feasibility, and to organise my finances to the point where I could spend time in the day on the game.
2014: I worked on the game more steadily during the daytime and I built lots of momentum.
2015: Now momentum is high, but my period of being able to work in the day has come to an end. I could take another six months off the project and build finance like in 2013, but I'd rather ship a game, and the Kickstarter seemed like a good way of freeing up enough time to finish it.