I found it FASCINATING upon rewatch to realize that Bellamy's original plan upon hitting the ground was simply to take Octavia and go. He never planned to stay with the other kids. It's only when Octavia refuses and then forces his hand by leaving with Clarke that he decides to stay, and that's when he comes up with the idea of removing the wristbands, as a way to ensure he's safe, and removing the wristbands is why he starts taking control of the camp in the first place. Once I realized that him fleeing in a later episode when it's clear the Ark is coming made more sense - it wasn't a spontanious, desperate decision, it's what he was planning to do all along. The difference is that originally he wouldn't leave without Octavia, but a few episodes later it's clear to him that Octavia doesn't really need anymore like she used to, so he takes off alone.