I think the unique thing about this story is that
we don't know for sure that he "fell" for it...or, at least we don't know what he fell
for, exactly.
There's the simplest explanation: that he, like the archetypical older, single, naive man he seems to be, fell for an online scam.
But most online scams don't end up with people in a foreign prison. The prosecutors argued successfully that he knew what he was doing, and the texts shown as evidence seem to indicate that he knew something.
But how much was that something? Did he go through the scheme because he believed his online lover was real and that this was just a task to prove his worth to her (and get them some money)? Or did he know everything? That is, he needed money and he figured that, unlike all those other dumb drug mules, he could use his history of seeming like an aloof nerd and make the case that he "accidentally" smuggled drugs across the border.
Layered on top of this is that we're reading this after he's been sentenced. He of course doesn't want to say anything revealing until he's out of jail, but he's retelling this crazy story even after it's failed in court. Which seems to indicate that he actually was bamboozled...and yet, what about those text messages? What about all those days in the airport, waiting for the e-ticket to Brussels that arrived too late? He never once was curious what was in the bag? Even the idiots in Dumb and Dumber looked in the bag.
This story is fascinating because I'm sure anyone who knows the professor even on a casual basis could spend hours at the dinner table trying to untwist the WTFs. It's a particularly great story because there are so many loose ends, but they are ends that are loose for very understandable reasons.