A significant part of the particular proposition of the Double Fine Advendture Kickstarter was also the development diaries and such they'd shoot.
It was not the game people paid for so much as the idea of the project as a whole existing in the first place.
Of course, I can't actually speak to the motivations of any backers, and there remains a great and oft-actualized potential for all manner of weird shadiness in the crowdfunding model, but in that particular case there was no reason for
>people [...] buy shit without knowing for a fact it is something they want
to necessarily be the case. The game was a result of the proposition, but hardly the be-all and end-all of it.
I've backed some of those anime kickstarters myself, not because it's a smart use of my very limited money, but because I like the idea, and it gives me a sense of investment in the end-product. It's like a low-risk form of gambling that allows you to pretend you matter, and that you're somehow contributing to the industry of a hobby of yours more than you otherwise would.
And if that just sounds like a madman's ravings to you fair enough, I'm first in line to decry myself as an idiot who should never be allowed access to money, because he'll just hemorrhage it all away in the most retarded ways he can devise on the spot.