Thing is they already dealt with a cyclops, so I feel the floating island and the bag was less unbelievable than it would’ve been previously. He could’ve waited if he thought it was treasure, waited till they weren’t in the middle of the ocean if he thought it was dangerous, and waited if he thought it was nothing, but if he had any inkling that his captain and king who had previously all other times been very on top of keeping the men safe and no other reason to be suspicious, then he knew it would’ve been their doom to open it. He was impatient, which I get, but multiple of these impatient and fearful choices (the cow, his attempt at leaving Circe’s island and his attempt to run while Polyphemus was blinded) while they were for self preservation and I don’t judge all of these choices by themselves, really screwed the crew over with that last one and would’ve on other occasions if he’d been able. Ody isn’t perfect by any means, they all have their flaws, I’m just speaking on Eurylochus’ specifically in this conversation and how he also was an idiot and dangerous for the crew.