Theory: Eddie made the movie to assist his colleagues
I personally think that this movie was made by Murphy for the purpose of securing a paycheck for his comedic icons/friends.
I think it was noble of him.
Richard Pryor and Redd Foxx were not having their phones ring off the hook with offers. In fact, it was Redd's last movie and I believe Richard's last significant role.
Take a look at some of the other cast. Call it the 'Schindler's List' of movie-making.