RE: Why doesn’t Ben kill a defeated Vader?
Jedi Knights are honourable and chivalrous. Killing an opponent in a duel is one thing, but killing a vanquished fallen opponent is something entirely different. That is an execution.
We already see that when Anakin ‘executes’ a defeated Count Dooku. It is a wholly evil thing, and not the Jedi way.
Again, nothing sustained anywhere in this tvseries that you just create entirely by yourself. Anakin should not have killed Dooku but he should instead have made him prisonner. Obi-Wan has no issue killing Grievous. Here, Ben just… leaves. It’s ridiculous and the only reason he lets Vader live is because Vader needs to be alive at this point of the story. The rest is just assumptions that you DON’T see in this tvseries.
As long as fans will continue accepting terrible screenwriting because they patch their own assumptions into huge plot holes, SW and other modern tvseries will stay that mediocre.