Typical digital lending programs are artificially crippled by publishers. They require libraries to purchase expensive licenses that are worse than physical books, like being subject to embargoes or expiring after only 52 lends.[0] This is why every traditional library's digital catalog is a tiny fraction of their physical inventory.
The IA merely allowed people to borrow books that exist in physical form with the convenience that modern digital technology allows.
Crucially, AFAIK digital lending systems aren't based on the number of physical copies a library owns; they're separate licenses. Thus, in a scenario where a physical library is closed but digital lending is still available, a significant portion of the library's catalog is inaccessible. At least in this regard, IA's logic is sound: practically-speaking, the number of copies of a given book that they lent during the period in question almost certainly never exceeded the number of copies held by closed libraries in the US.
Every library I’ve used in the states (from rural Georgia to Seattle metro) already has a digital lending system.