Cook is simply rewriting history. There was a big demand for MP3 players at the time apple released its ipod, it only took apple several generations to get it right and sell any significant amount(mainly due to bad design decisions).
Where did Cook say there was no demand for MP3 players? He said people didn't think they needed an iPod, which for many was true.
Before the first iPod, music players were awful contraptions made of cheap plastic with infuriatingly bad software and controls and ridiculous designs mimicking portable CD players.
When the iPod was first announced, Apple haters (and those whose business was threatened by the iPod) ridiculed it with the usual dimwitted complaints about high price, lack of user replaceable batteries, lack of support for every obscure audio format, and the requirement that its music be managed with Apple software rather than via third party software or "simple" drag and drop file management.
Those complaints proved to be wrong, as they did when they were hurled against the iPhone a few years later. They sound very familiar today.
Although the iPod didn't achieve instant sales success (this was a different time for Apple and few people knew much about the company outside of computer circles) it was readily adopted by those who realized what it offered - a beautifully designed pocket sized device with huge storage, an easy to manage library, and a radical new easy to use interface.
In the years that followed, the iPod's design and capabilities improved while more affordable price points emerged. Not only did the iPod prove hugely successful, but it acted as a gateway for people to experience Apple's quality and design philosophy, prodding many to buy their first Mac (yours truly included.)
If that isn't a success story, I don't know what is.