thinking about how orpheus turning to look back at eurydice isn’t a sign of mortal frailness but a sign of love
“Eurydice, dying now a second time, uttered no complaint against her husband. What was there to complain of, but that she had been loved?”
― Ovid, Metamorphoses
This is true no matter the version you're reading.
1. Eurydice trips and Orpheus turns to help her because he loves her.
2. Orpheus cannot hear Eurydice behind him, and fearing that he's been tricked, turns to make sure she's there.
3. Orpheus makes it out of the Underworld, and so full of love and excitement to be with Eurydice, turns to embrace her, forgetting that they both need to be out of the Underworld.
No matter what happens in the story, Orpheus loses Eurydice because his love for her compels him to look.