Have you ever negotiated with kidnappers? They can call now and won't call till tomorrow. They are keeping the victim to get the best deal. They can even keep a victim until cars or other valuables are sold. Some victims have stayed with kidnappers for one month.
I agree with you on this. When my father-in-law was kidnapped, that was the same hell we went through just to get him out and seriously, the story might sound formulated but believe me, it's a very horrible experience to be either kidnapped or be the one to negotiate with the kidnappers because your every action or inaction determines whether you get to see the loved one who was taken or not.
The issue with the banks updating your sister-in-law's account was really fast cause it was as if they understood how important she needed that update because I know how intense it was for me when I needed to update my bank details, the back and forth was hectic.
I'm happy to hear that your brother is back in one piece, at least even though he had a broken leg, it is better than being killed despite taking the ransom.