Was the VM a failure?

[magnesium]

I wouldn't say that the VMS was a failure. The crucial question seems to be whether or not it was ever intended for distribution. Encryption without any reference to the method in the manuscript itself (as in other encrypted manuscripts) suggests that it was not intended for distribution in the first place. There is still the possibility that there were clues on the missing pages of the manuscript, but I think this is rather unlikely. In my opinion, it can therefore be assumed that the encryption was generally intended to make it impossible for others to read the manuscript. The use of the VMS was therefore reserved for a few insiders. The question arises as to what was so explosive in terms of content that it was thought necessary to conceal it. In any case, the illustrations do not suggest such an explosive nature. On the contrary, if the content is related to the illustrations, which is to be assumed, then we are dealing with rather trivial topics. One could assume that the encryption was more of an end in itself, a kind of intellectual “finger exercise”. So it does not seem surprising that the (experimental) method did not spread further, as it would have had to be disclosed.

I'm inclined to agree. If the VMS is a ciphertext—which is not confirmed, but is historically well-grounded—there is no reason to expect that it was meant to be a cipher meant for wider uptake à la Alberti or Trithemius. Depending on the creators' assessment of how dangerous or explosive the contents were, making a cumbersome one-off cipher for themselves to ensure the impossibility of other people reading it could have been worth it.

On the note of a "finger exercise," I have sometimes entertained what I call the "Skunk Works hypothesis": that the VMS represents a deliberate, high-investment exercise to create a state-of-the-art cipher relative to its peers, but the resulting cipher proved clunky enough to use that it was not adopted by the cipher's benefactor. On the balance, this hypothesis is almost certainly wrong; you don't need to make an entire encrypted manuscript to prove your point when only a few encrypted letters would suffice. But it is fun, for much the same reason as the "Ocean's 11 hypothesis" (aka the collaborative-hoax-as-elaborate-scam hypothesis)—it invites compelling narrative.