Mosaics

I'm working on a mosaic novel, because it amuses me to do so. It started with a story I decided to write purely because it amused me to do so. That story turned into a 20,000 word novella about Misha, a secondary character in my Huge High Fantasy World. It's a good story, and I got a lot of positive feedback on it. So I decided to write a story for several other characters that appeared in Misha's story, using those stories to form a narrative in negative space for Vittore, brother of Misha and one of my favorite characters.
It's been a fun challenge, since I'm using the Misha story as a template for the others, but having to make sure they're all unique. But I'm needing to understand what made the original story successful, and why some of the subsequent stories are feeling boring. My revelation of the morning is that Misha never took the easy way out, so in subsequent stories, when I find a character making an easy choice, I have to consider whether it's lazy writing on my part, or if it's a genuine flaw in the character that they'll overcome or be overwhelmed by.