lead poisoning from pipes did not cause the downfal of rome

So some very bright person I overheard today was telling a friend in loud english that lead pipes destroyed the roman empire because they all went mad and down went Rome. So aside from that being absurd for lots of historical reasons it's also chemically unlikely. As many of us may remember from the REACTIVITY SERIES of METALS. Lead is way way less reactive than calcium, so so It could never displace it from solution. Roman water has tons of aqueous calcium in it, and it would actually cake over the inside of the pipes because calcium oxidizes with water really easily. So it's very unlikely that enough lead would be exposed to get leeched into the water to drive the entire ruling class of a large empire mad. And yes, I'm a bit of a nerd