He probably talked about his wealth to the wrongs people and they've then set up the kidnapping to relieve him from his funds.
The fact that they still killed him after the ransom was supposedly paid is pretty terrible, but also somewhat logical actually.
it is my understanding that he was somewhat known in that part of the world. I read somewhere on the caisno forums that he was often flashing with expensive cars etc. Nothing wrong in doing that, but as you propose it definitely has something to do with the ransom and death.