The lifeblood of most business websites' SEO interests is the backlink profile they accrue over their years of existence. Google considers the number of referring domains featuring backlinks that point to a given website to be directly representative of public interest in what that site has to say and offer to its audiences. Thus, if the website has a strong backlink profile, it will be much likelier to appear in the initial pages of various SERP listings. Backlinks are generally placed willingly by the owners of other domains and left at those spaces without any further thought paid to them, which means that most of them will keep pointing to a website's domain even in the scenario that the website is taken off the Internet and its domain is considered to be expired.
Expired domains offer a unique appeal to webmasters who plan to find easy support for their own websites pertaining to the industry that was once discussed by the websites that used to be located at those points in cyberspace. The incentive to buy an expired domain lies in the fact that all the backlinks still pointing to it can be made to support the backlink profile of the other website through the use of 301 redirects. This will end up giving one's own website a potentially massive head start in its efforts to secure a solid position in the SERPs in reasonable amounts of time. Since multiple websites will likely clamor for that valuable space, the process of purchasing this domain plays out similarly to an auction.
However, the webmaster may need to perform a lot of extra work on their own website if the website originally located at the expired domain was composed of a large number of pages. The webmaster's site would have to feature a separate page corresponding thematically and content-wise to each of the defunct website's pages so that link juice can be transferred on a page-to-page basis without penalties from Google. Meanwhile, Google is prone to penalizing a website's rankings if too many different expired domains are redirecting to it. For more information click here https://www.reddit.com/r/SEO/comments/db7oe5/expireddomainsquestion/.