_Washington Post_ just had an article about why (https://www.washingtonpost.com/opinions/2025/10/12/america-r...).
"In 1984, a German historian compiled 210 explanations historians had suggested for Rome’s fall, from lead poisoning and barbarian invasions to Christianity, moral decline and gout.
After studying dynamic civilizations such as Athens, Rome, Abbasid Baghdad, Song China, Renaissance Italy and the Dutch Republic, I can attest that there is no single explanation. Each golden age had its own character and its own downfall."