Thanks for sharing your thoughts. Having been present for his testimony as well, I had many of the same impressions as you did about his character on the stand. The only difference is that I wasn't surprised by it. I was surprised that he testified, but I expected him to show his best form to the jury. If he had gone up and behaved like Noudga did, he would have certainly done himself in.
Having some familiarity with game theory and the dynamics of cut-throat defences, I viewed Smich's testimony as a textbook play to save himself and roast Millard. It started with Dungey introducing him to the jury by saying, "We want to give you the full picture of what happened," and then proceeding to paint him in the best light possible by highlighting positive points about his work history, his dedication to his family, and how he completed his high school education while incarcerated. They even sugar-coated it by introducing his criminal record to show that, despite how amazing of a person he is, he did get mixed up in some bad things: he sold drugs, he stole things, etc. The crux of it all was to create the impression that Smich was a petty thief who was mixed up in a bad lifestyle, but despite this he was always a good guy who would never hurt anybody. From that basis, the story he would tell about the Bosma event would be much more believable.
In the end, I am left with the impression that Smich was not a scheming manipulator like Millard was. They wouldn't have been so compatible with each other if that was true. Rather, Smich looked up to Millard and developed a strong attachment to him like so many other people did. Smich was in a bad place: he was a dropout, he was addicted to booze and cigarettes, etc., and Millard offered him the support and the opportunities to make something of himself. (Note: I find it ironic that Millard wanted to help Smich get off drugs and alcohol, but he also seemed to be his main supplier). There was a real love between them and they expressed it to each other regularly.
At some point, they discovered a mutual thrill in stealing things together. I say thrill because IMO neither of them were desperate for money the way a crack addict might hold up a convenience store. They didn't need to do the things that they did, but there was an excitement in it which became an addiction of its own. As Smich wrote to Millard, "I'm ****in hungry for a mission." There was a clear excitement in these missions, particularly on Smich's behalf despite Millard being the so-called leader. Their addiction to the thrill drove them to escalate their criminal activities over time.
Everyone will draw their own conclusions as to how far they went in pursuit of the "thrill", but in my own opinion, they both discovered a thrill in killing people. Sadly it took three murders before they got caught.
