The introduction of lowercase was a disruptive technology much like printing or digitisation or the cloud, and it resulted in the wholesale discarding of earlier, bulkier majuscle manuscripts. There is a cute story relating to the manuscript history of the Vita of St Andrew The Fool (Andrew of Constantinople).
The Vita purports to have been written in the 6th century, but there are enough anachronisms to suspect it was actually written in the 9th. The editor of the text Lennart Ryden found a single leaf of the text, used as padding in the spine of a later manuscript. It was in all capital letters, but they were 9th century capital letters — which was odd, because by then lowercase had been invented, so noone would be writing in all caps.
Ryden thinks that the leaf was from the original manuscript. The author wanted to pass it off as a 6th century text — from when people wrote in all caps; but he didn’t realise that the uppercase he was familiar with in the 9th century had changed from what was used in the 6th century. The forgery was so successful, that the original manuscript was copied into normal lowercase — and thrown out; that’s how a stray leaf ended up as padding.