Everyone gets this wrong

[Mahaloth]

@Dewey_Finn

I thought that the Grail acquired the powers only after being used to catch Jesus’ blood as he was hanging from the cross? So it was not magical during the Last Supper

I have no idea. I don’t think the movie suggested this.

Here is the script. I guess that is the emphasis in it.

Across the desert and through the
mountain to the Canyon of the Crescent
Moon, to the Temple where the cup
that --"

           Suddenly Indy stops and looks up at Donovan with a startled 
           expression.

                                 INDY
                     "Where the cup that holds the blood 
                     of Jesus Christ resides forever."

                                 DONOVAN
                          (reverently)
                     The Holy Grail, Doctor Jones. The 
                     chalice used by Christ during the 
                     Last Supper. The cup that caught His 
                     blood at the Crucifixion and was 
                     entrusted to Joseph of Arimathaea.

           Indy rubs his chin with a dubious expression as he takes the 
           glass of champagne Donovan now offers him.

                                 INDY
                     The Arthur Legend. I've heard this 
                     bedtime story before.

                                 DONOVAN
                     Eternal life, Doctor Jones! The gift 
                     of youth to whoever drinks from the 
                     Grail.
                          (beat)
                     Oh, now that's a bedtime story I'd 
                     like to wake up to!