The fact that the thugs are surprised by the appearance of Thunder Girl tells me that the kidnapping doesn’t have anything directly to do with her, or at least that they didn’t know she was involved.
That does leave open the question of what it was all about. A father unhappy with the custody arrangements? An enemy of the child’s parents? A simple case of human trafficking, selling babies?
Whatever it is, these guys don’t look prepared to take on a super. They’re going to regret picking this baby at this time.