There’s a good case for the theory that the Romans were destroyed by plumbing: they had hot and cold running water in every wealthy Roman’s home. The word plumbing comes from the Latin word for Lead, Plumbum, because all their pipes were made out of lead. Next to gold it is the softest and easiest metal to extrude pipe from, and gold is too expensive to use for the purpose. The Romans were great engineers and very advanced for their time, but not advanced enough to know the dangers of heavy metal poisoning to the human brain. It occurs so slowly that people didn’t notice it was happening for a long time but it eventually causes severe mental and physical impairment. Because only the rich could afford plumbing, it affected the roman Leadership class, leading to progressively more insane behaviour.
The Roman aristocracy ‘Plumbed” the depths of depravity after their Plumbers plumbed their palaces with lead.
Electing a Horse to the Senate was an early symptom, fiddling while Rome burned was another, but the maddest of the lot was replacing Roman citizens in their Legions with foreign mercenaries: it was madness to out-source their own defence to contractors. From that moment it was only a matter of time till the Empire fell.