Getting ready for the test I found this task
The lucky coincidence allowed them to take a trip together and Angela loved traveling! More than that, she ________ (prepare) a list of the most desirable destinations. It was all written on her tablet and it was time to start making those dreams come true!
The key states that Past Perfect should be used there but I'm wondering why. I understand that maybe the result is emphasized there but I can't see any certain evidence for that.
My question for native speakers is whether it is grammatically correct to simply use Past Simple in the abstract given?