Stale, forgotten content often resurfaces through search engine scraping,...

https://stateofseo.com/should-i-301-redirect-old-urls-or-leave-a-404-the-reality-of-content-decay/

Stale, forgotten content often resurfaces through search engine scraping, hurting your current site’s authority. When outdated pages reappear in search results, they confuse users and dilute your SEO efforts