Software estimation nightmare

I have seen a few estimation nightmares in my time and have been unfortunate enough to be in some of them. Let me narrate a few anecdotes first
Anecdote 1:
I used to work with a re-insurer. This company had a legacy application that was written in fortran. Yes fortran. It did some very important things. It was capable of making estimations for a given market and it crunched a lot of numbers into meaningful data. Because this application was written in fortran, finding the right engineers to maintaining it was difficult. So they decided to shift the application to a better supported platform / language.
The work came to IT and a manager said ‘Lets convert it to VB’. This person, did not know fortran and was not a master of VB either. No developers or architects were asked for advice. It was simply decided that the application should be converted to VB from fortran.