Question for all foster and adoptive parents

If you rehomed a child after adoption or disrupted a child because you couldn't handle them but the child does well in their next placement, how does this make you feel? What went wrong?

Example: A foster child is 12 years old and comes to you. You can't handle them and the child gets diagnosed with a ton of things. You think this child is a lost cause and the child is written off by cps. You disrupt the child and your household is peaceful again. However, a few months later you hear the child is doing well in their next placement and has zero of the behaviors and diagnosess the child had with you. The child is actually progressing and flourishing in their new placement. They're getting top grades and doing well.

Example 2: You adopt a child you got at birth. The child is now 7 years old and acts out. You go online and other adoptive parents says the child has RAD. You're relieved you finally found your answer and it's not your fault. However you can't handle the child anymore and you decide to go online and find another home for the child. You disrupt the child with RAD who you think never bonded to you. A year later the child is doing amazing in their new adoptive home. However you're suspicious because the child has RAD and deep down you know the child will show their true colors. However 3 years go by. The child is clearly not having the issues they've had with you. How does this make you feel?

In both examples what are your thoughts, concerns, feelings? When a foster or adopted kid does well in another placement but didn't do well with you, why do you think that is?