The last line where you stated that most project dump their coins is actually true. They are projects that people call "scam projects". All they do is run an ICO, release some crappy tokens and then once they have gathered enough money, they dump their tokens on the market to gain whatever they can and then finally runs away.
You will find hundreds of such project. Sadly, there are people out there who still falls for this kind of scams.
Even if the project are legit, it is just unfortunate that they will also dump, scam project ruined the reputation of ICO and worse it reach to the crypto market now, and that is the reason why even in IEO, a project is struggling to raise the funds they needed.