The reason why Tau is a fundamental number is because it is the Identity Operator for Rotation. Pi is lacking in such fundamental utility.
Tau is as fundamental to Rotation as Zero is to Addition and One is to Multiplication. Tonight I watched several YouTube videos about Tau and I didn't see anyone make mention of this fact. Bob Palais wrote an excellent article back in 2001. But the arguments that I've seen favoring Tau over Pi were basically a matter of style and taste.
The reason why Tau is worthy of primacy over Pi is not because of any such artistic reasons, but because of this fundamental mathematical reason.