The failure of windows phone had nothing to do with 'developer engagement'. Simply put they were far too late to market to compete with the already established iphone & Android.
They might have had a shot if they had realized it and focused from day one on the business market (which they were already a player in), but instead attempted to compete with Google and Apple who had more cachet with consumers.
Keep the number of passes in a compiler to a minimum. -- D. Gries