Scott Peterson didn't think his crime would garner all the attention it did, either.
And JVDS is a only a 17 year old sociopath, vs the the 30+ year old sociopath from Sacramento.
I think Scott must have known that Lacey's family would give it all the attention in the world, and that he would be suspected by the police. That is why he TRIED to contrive an alibi. He could not have suspected that Fox News, CNN and other Media would go so crazy over the story.
As for these criminals on Aruba, they are in a tighter spot than Scott Peterson, in a way, in that there is no way a young high school girl from America on the Island for a Senior Trip, is going to be allowed to be murdered or kidnapped or whatever and not a huge spotlight be shining on that Island and surrounding areas day and night until what happened to her is revealed. People saw who she was with. There were witnesses.
Van der Sloot and the brothers know the heat is on them. If they cannot explain what happened to Natalee, then they at least have to throw suspicion on others, and if that does not pan out, then the suspicion goes right back to them. They have important family connections, friends, associates, etc. who come under the glare of the spotlight. And if someone they barely know, but have had some kind of interaction with, has taken Natalee, those connections will be pursued, too.
If anyone thought this would be some kind of anonymous crime, in that very public situation, in such a confined set of circumstances with witnesses, to boot, they were very stupid.