If you look at all those different aspects that play a role in human decisionmaking, then you see that it would easily get way too complex and inneficient if you would be mr darwin and you would want to organise this whole proces within a brain.

That makes me think that creating a special 'program', a concept such as 'free will' may be the easiest way to organise all these processes simultaneously.

You have all these different levels where things happen that may be relevant for the outcome of the proces. What if you would have one program that brings all of these levels toghether somehow?

You would no longer have to run a feedbackprogram on all of these separate levels but only on this free-will program.

It makes sense to have such a program, but that program should not be very complex itself, because that would only increase the chaos in the whirl of data that's going on here.

To create a concept that is simple but that would at the same time fit this whole structure of a one-level program that brings different levels of a multi-layered information proces toghether on wich you can run a feedbackproces to check for errors and so on, in  a social creature, a program that would include some form of accountability would be the easiest, most compressed solution.