Well, there are a few factors in play.
For one thing, a project without some real names of the players involved, and without some sort of reputation behind one or more of those people or the company, is unlikely to be funded in large amounts. An awful lot of people who back Kickstarter projects tend to look for return projects. I tend to watch board and card game projects, and a great deal of them are either established (though small) people or companies, often who have previous Kickstarters. And people do check you out – if you aren’t who you claim to be, for example by giving a false name, it tends to get discovered as more money gets involved. Potential backers do investigate you and your claims.
On top of that, there’s a certain level of work involved. People expect things like videos showing prototypes, photos, schematics, whatever. In games, for example, it’s expected to show a copy of the rules, example art, prototype photos of the game, and so on. If you are a scammer, how much work are you going to put in for this? Are you going to develop a game, playtest it, work on it, create marketing materials for it and a video, all for a few hundred bucks (not an atypical amount for a first time, small game)? With all that work, you might as well get a job.
It’s not to say you can’t scam people, in other words, it’s just that it’s not that easy. It’s not a matter of writing a paragraph description and raking in bucks – there’s significant legwork involved for most large projects – and the returns are unlikely to be good if you’re not backing up your claims. That said, it has been done, as in this case (though this was caught by Kickstarter before being funded):
In that case, though, the system worked - the funds never got there.