Having way too high costs for production for its products.
Mismanagement.
Till 2001 Sony ruled the consumer electronics world.
Then Samsung took over in a crushing way.
Sony is just a shadow of its former self.
There are even electro shops in Japan that dont even sell any Sony product any more.
https://www.google.nl/amp/s/www.itworld.com/article/2887089/sony-is-effectively-no-longer-an-electronics-company.amp.html
https://www.google.nl/amp/s/kotaku.com/5960411/how-sony-is-turning-into-a-ghost-in-japan-and-around-the-world/amp
https://youtu.be/eSHgFkYEb2o
''Hadouken!''