It is simple, they made the money and then majority of the projects vanished, you really cannot trust any of these projects promoted by these sites and i never trusted any projects for a long time, i am promoting a project after a very long time because one user took time to compile a list of trusted projects and i am sure he is not having any vested interest to compile the list.
Right, sometimes the rating given by the website can be manipulated according to the wishes of the project owner if they pay a certain amount. This makes the rating or review given inaccurate. This trick is often used by scammers, we must be careful and not easy to believe it.
These are very common tactics in business because every one want to go very fast and these things happen in this case we have too many fail projects which run away with very good amounts and no one able to catch them or bring them in court so doing some own search is much better and good option.