For further info, if anyone is interested, Stephen Bax claimed a decade ago to partially decode the manuscript; here’s a video with his reasoning, as well as the paper he released. Sadly Bax passed away in 2017 (may he rest in peace), so the work was left incomplete.
I also read the theory, that during the time it was likely written there were a lot of rich merchants and noble men with an interest in the occult, magic etc. So it could be a hoax to sell for a high price as a magic book. After all, there was a flourishing trade in religious relics. Not too far fetched to think that someone who maybe even had the necessary education to make and write books could make up a fake “magic book” and sell it to superstitious duke for a fortune.
That is part of the mystery for sure. If it is a modern - or at least later - hoax it’s the work of the best forger in history. All physical and historical evidence points to it being created in the first half of the 15th century. It also points to multiple people being involved in making it. And the complicated rules and structures of Voynichese involve an awful lot of effort for a medieval scam.