They each had longer runs than we’ve had.
My pet theory is lead. From 1950 to 1980 we birthed a leaded generation [1]. Today, up to 60% of American voters were born before 1975 [2]. (Voters born between 1950 and 1980 came into the majority in the 1990s and should fall into the minority by 2028, but only barely. So in summary: Iraq War, Financial Crisis, Covid and Trump 47. It won’t be until the 2040s when truly unleaded voters, those born after 2000, command a majority.)
[1] https://pubmed.ncbi.nlm.nih.gov/35254913/#&gid=article-figur...
[2] https://www.pewresearch.org/politics/2024/04/09/the-changing...