Initially when Bitcoin was released, the developers’ motive of inventing bitcoin was not to replace fiat currencies, but to introduce a safe and faster network of transaction of money without rates of central bank. However, as the years progressed, bitcoin was seen by holders as a means to escape the fiat currency controlled by the Central authorities. This is when people started developing the idea that coupling of bitcoin was a big mistake. Personally, I do not think it was a mistake. The developers did what their goal was, which was clearly not to replace fiat currency. 

In the present date, it will need an official declaration of the developers of bitcoin to decouple it from fiat currency. This will result in an unimaginable crash of BTC market cap and value, as till date all of it was dependent on fiat currency.