The short answer is
So, why is it on the Internet Archive? The likely answer is that the Archive operates under a policy. The site allows users to upload content, but it will remove any material if a legitimate copyright holder files a formal complaint. The existence of the Leave It to Beaver collection suggests that the rights holders have either not filed a complaint or are not actively policing this particular upload. Leave It To Beaver Complete Series Internet Archive
Leave It To Beaver focused on simple childhood dilemmas: getting a black eye before school pictures, losing a haircut fee, or trying to buy a pet alligator. The short answer is So, why is it on the Internet Archive
The life and career of Hugh Beaumont (Ward Cleaver) is documented on The existence of the Leave It to Beaver
was unique for its time because it prioritized a child’s perspective over adult drama. Creators Joe Connelly and Bob Mosher based the show on their own children—Connelly's sons Jay and Ricky were the primary models for Wally and Beaver. Although it never cracked the Nielsen top 25 during its original run, its presence on the Internet Archive today proves its lasting status as a "defining" depiction of postwar American life.