Big AI mostly switched to synthetic training data anyway. The books they're digitizing are being used to gather knowledge, not writing styles or logic (mostly).
As in, when you ask ChatGPT how long some book is, it can just go check (if it's in the database). It's also useful if you ask about that book or about knowledge contained in that book. It'll even reference books now (if you demand that in your prompt).
It's not the same as earlier LLM tech which relied on scanned text to figure out how to respond to any given prompt (from a language standpoint). The "language" part of LLMs is a solved problem now (thanks to the synthetic training). At least for English 🤷

Yes. That does make sense.
If you bought a book, scanned it—destroying it in the process—then read it on your computer, that would be completely acceptable.
Why is it wrong when a corporation does the same thing?
They're not claiming ownership of the copyrights, just ownership of a copy. Which is how copyright works.