Kickstarter isn't selling, though. It's giving a company some money in the hopes that they'll be able to make the thing they want to make and give you one of them for free in return.
That's one interpretation. Another is a company is selling a product they don't have yet, but they will sell it to you when they have it. It's not your problem if they can't make or deliver what they sold, it's their problem. Up to a court depending on the amount at stake.
If Kickstarter were purely about pre-payments for guaranteed products it wouldn’t exist. Outside of deliberate fraud, lots of companies try to deliver things that they end up being unable to do so.