The Force ghost part of star wars has and always whills be a subject of much debate.

I always felt Yoda and Obi-wan were handled well as in their deaths and their ascension. But I never felt the same way about Vader / Anakin

In that much Ray afraid is right the more you try to apply some form of explanation to “Force Ghosts” the less mystical it is.

We don’t and should not have an explanation of how or why only the thread of where it came from, and why only certain Jedi could attain that special ability.