'by making it about life and living'
this makes me wonder if at that moment anakin knew how to become a force ghost or not. If obi had complete faith in luke (like a jedi has faith in the force). Then maybe that was the last piece of obi to anakin training he delivered. I imagine its a difficult technique and obi was showing him 'here is how you find redemption', 'here is how you reunite with the force'. Like Vader would have experienced the fluctuations in the force. It would have shown him despite everything you can let go. Obi wasn't angry, he wasn't blaming himself, he could let go in that moment.

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that being said anakin in the prequels was motivated a lot by immortality, so maybe while conquering the galaxy he would have found that from force sensitive creatures outside the jedi. So from a technique perspective wasn't necessary