Because Twitter potentially bears liability by hosting them into the future, and is only willing to bear that liability if you agree to their terms.
Citation needed. If they receive a copyright takedown request and don't act on it, then they're liable. Otherwise I don't see where liability comes into play. Please cite court cases showing websites are liable for content posted by its users. Nobody is using Twitter to archive copyrighted material.
It may not be for content, but for user data analysis without consent.
Then don't analyze those records... such nonsense.
Indeed.
This is the exact purpose of Section 230 and why it is so important to preserve it.
Except that Section 230 explicitly states that they don't bear liability.
Does European privacy law have the same provision? They are removing non-US accounts first, after all.