You know, sometimes when you look back at a case, you do so with the benefit of hindsight. And people's actions are then harder to explain. But you need to put yourself in their shoes at the beginning of the entire ordeal. This is 100x more important when the case becomes a national obsession, or at least gets a massive amount of unexpected attention.
Sometimes people get ideas that, while clearly wrong and illegal, don't seem so crazy at the time. They are looking for a quick buck, or perhaps some much needed attention for whatever reason (professional, personal). You expect a bit of trouble, a few days or a week of heat, but it all blows over, and eventually, mission accomplished! Your small time scam worked, you walk away with a bit of cash, attention, whatever.
But occasionally, albeit rarely, the unexpected happens, and your crime becomes a national obsession, even appearing in newspapers around the world! You are thrust into the spotlight, you now need to explain things in much more detail, the scrutiny is overwhelming. "How did this happen?" you ask yourself. You expected some local attention, but that was manageable. But TV interviews? People looking into your past? Examining in detail previous jobs, statements, personal details. All of a sudden, this simple crime is not so simple any more...
People look at you and think, "Why would he/she do that, knowing the kind of trouble it would cause?" But of course they never anticipated this level of scrutiny when it all began. It seemed like the perfect crime at the time...
Or, perhaps put more succinctly: oh what a tangled web we weave...