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It always amazes me sometimes, how things in my story change as I edit them.
With a short story I wrote last year, when I went through edits and it barely changed content wise. It was tighter, better written, and flowed more smoothly and I did add a decent amount of new content, but the core story and what the characters were doing didn’t really change all that much.
However, I just finished editing the newest short story and most of the content has changed. Certain aspects of why a character was doing something or what they were doing specifically had changed. It’s better for it, but it just amazes me some with how different it ended up being compared to the other story I edited. Though I also ended up having a secondary character take over briefly and insert herself in the beginning of the story rather than just have a tiny space in the end of the story. But I also think she deserved that addition so I gave it to her.
Meri's Corner 
I think sometimes it’s just the nature of the story. Sometimes editing totally changes it, and other times, it turns out it doesn’t need much editing. It might have something to do with the state of mind you were in when you wrote the first draft.
I think you’re right, on all accounts. I ended up diving deeper into the characters while I was doing the edits on the second story, which also added to changing. I don’t think I really got into the meat of the characters before edits either, But with the first story, I was deep in my characters while writing the first draft.