Why did nokia fail?

I remember everyone had a Nokia. They were so strong! But they were too slow when new phones came. Like the iPhone.

Nokia stayed with their own software, Symbian. It was old and not good for apps. Apple and Android phones were much better for internet and apps.

Then they tried using Microsoft's Windows Phone. But it was too late, I think. No one made apps for it. The phones were good, but the software had no support. So everyone just bought an iPhone or a Samsung instead. They did not change fast enough.