If everything checks out, then OP is an idiot.
Responds to an ad on Craigslist and tells them to meet him where he's staying
Was getting caught part of your plan? Seriously, if the guy recognized him and called the cops, then there would be no place to go, because his hideout is already found. Also, another guy in the thread could post something, then just tell the cops where he's staying.
Gives out Skype to the internet
If he moved and logged on without keeping his proxy on - he's done for. There's a bunch of sites that will resolve an IP from a Skype username. If he has Skype on his phone, and no proxy, then he's done for. Also, now the cops can just call up Skype and say "Hey, we need the past IPs of this username." After a bit of work, they could find out where he lived and who he is. It's how a lot of people get swatted. If some script kiddies on the internet can do it, then I'm pretty sure a federal organization that's trained in this kind of stuff can do a lot more.
Posts everything, including plans and ideas, on the internet
If the FBI is watching those threads, they now know exactly what his plans are. It's impossible to stay two steps ahead of your enemy if you're telling the audience what your next trick is. Telling the internet what he's about to do is enough for the FBI, or whomever deals with this stuff, ample knowledge and time to set up a trap, or nudge him into one. On top of that, each unique thing that he does is enough to give them another lead. He buys a bike and posts a picture of it? Now they know which Craigslist user to question, so they can get even more information about him.
The guy on Reddit made this look so easy
He also didn't post his plans on the internet and then came back to brag about it. The fingerprints and pieces of hair that you leave at the scene aren't the evidence that's going to get you caught; it's what you willingly divulge to people on a whim.