The refusal of the majority of QM theoreticians to accept MWI is the root cause of the "mystery".
I'm sure decades after Copernicus, there were still astronomers going on and on about the complex interplay of the wanderers, and how the retrograde motion could only be explained with circles up circles, and spheres upon spheres.
And Copernicus was still wrong about the ontology and there are many critiques of MWI not just by people scared to accept its metaphysical weight.
I think it's unfair to criticize too harshly those who aren't ready to dive in with MWI. It's not that incomprehensible or too crazy, but it is far beyond what current physics says exists. We'd go from spacetime to some infinite or extremely high-dimensional space. Why should we need to go that far when other interpretations maybe ask less of us.
Why bother with a 3D model of the planets when a 2D model of circles upon circles asks less of us?
It's so much simpler to model the wanderers as moving along the surface of a celestial sphere! Adding depth adds nothing to our understanding when the current mathematical models can already predict their motion to high accuracy. It's all isomorphic anyway.
Look, just go away with your heretical notions, I have calculations to perform!
The refusal of the majority of QM theoreticians to accept MWI is the root cause of the "mystery".
I'm sure decades after Copernicus, there were still astronomers going on and on about the complex interplay of the wanderers, and how the retrograde motion could only be explained with circles up circles, and spheres upon spheres.
This is no different.