Because some of the employees were well known and who had proven track records with well loved games. It was a very early kickstarter so there were a lot of unknowns with the project and how it would work. I suspect there are a lot of backers who think it was a success because it helped revive interest in the genre and help other game companies learn from the mistakes.
If it was just Broken Age, I could see people giving them another shot, but when you combine that with the broken promises of Spacebase DF-9, I can't fathom trusting them to fulfill a Kickstarter or an Early Access game. With Spacebase DF-9 they took $400k in investor money from The Indie Fund, Humble Bundle, and a few others and made it back in two weeks. When sales slowed, they stopped development with a lot of promised features not finished. Sounds like a hell of a good deal for the investors, not so much for people who bought the game, trusting that an established developer would actually finish it.