It was curated, but not by the Librarians of Alexandria. The curation was done by travellers who decided that particular books were important enough to bring with them.
Incidentally I've imagined the Librarians scrambling to grab books from the shelves as the Library burned, and wondered if they would have actually "saved" anything.
The idea being, anything the librarians thought worth saving probably existed in other libraries, and would be more likely to have multiple copies survive to this day. Meanwhile, if they grabbed some book of third-tier poetry at random, that would be more likely to be a unique volume.
Along the same lines you could argue that any book collection is being curated by writers, as it's the writers who decide what books are important enough to write.
The idea being, anything the librarians thought worth saving probably existed in other libraries, and would be more likely to have multiple copies survive to this day. Meanwhile, if they grabbed some book of third-tier poetry at random, that would be more likely to be a unique volume.