From what I've read;
>How often do the ransomers actually keep their promise after getting the money?
Usually keep their promise ....because they need the next target to believe that they will honor the deal??
>Are they ever caught and brought through the legal system?
Occasionally. National law enforcement (FBI, etc) partner with the ransomers' host country's law enforcement IF they find them. I've seen more partial money 'clawbacks' than arrests in the headlines.
>And is there insurance to pay the ransom?
IIRC, my small business policies began to exclude ransom & hacking. You could buy $$$$pecial riders, of course.
>And if they do pay the ransom, doesn't it just make ransomers ransom more?
Yes, I think so.