How did they work? They did not "crack" Deezer using a master key. Instead, they exploited an early API flaw:
The derived Blowfish key is applied to the encrypted blocks using the specified IV to return the audio to its original clear-text format. Hacker News Developer and Security Context Official Tools: Developers can use the Deezer for Developers portal deezer master decryption key work
: This key is essential for the actual deciphering of the music data. The encryption used is often a simple XOR cipher applied to the stream data in chunks. How did they work