Nokia Failed because of a number of Reasons some of them are

1.) They failed to develop or adopt an OS that was as user friendly as Android. At a later stage when it was bought by Microsoft the OS they put in was too complicated to handle for non-technical people. Plus the Android Play Store always had more new Games & Apps in it than Windows had.

2.) Nokia was known for its innovative designs but lately they had become followers of what Samsung or Sony or Apple bought on the table. The innovative original designs of Nokia 6600, 6630, N8 , Communicator had all become history.

3.)Competition from other new mobile manufacturing companies such MI,Micromax etc. These new phones cost a lot less than Nokia and provided much more features than Nokia courtesy Android.