'Scientific sounding' is pretty much the nail on the head there. People have a tendency to believe authority figures, whether the information they have is correct or not - we listen to our Doctors, we generally do what the police tell us to do, our teachers know more than the students they teach, and you may have heard of the Milgram experiment, which really pushes how far this obedience can go.
With regards to 2012, or even pseudoscience in general, you'll see proponents banded about as self-proclaimed experts. In that one word, expert, we're led to believe that they really do have something to say. I can only really speak for Sitchin and the Nibiru crowd, who see him as an expert in his field simply because he knew more about Sumerians than the YouTubers who cite him. The only problem is that he was a poor choice of authority to follow on the subject, but you'd only know that if you stepped outside and look at the claims from another angle.
Set yourself up to be any kind of authority on a subject, even to the extent of being in contact with aliens, and you put yourself one step higher than the audience you have, who in turn reinforce your 'authority' - you don't have to know anything complex, you just need to know more than your audience.
