Happily enough, he spent his money charitably, building fourteen hospitals, three chapels, and seven churches. Alchemy is about making gold. Take something inexpensive and easy to come by, like mercury or lead, and by means of obscure knowledge, transmute it into gold. Now that's added value. Unless you are a physicist, though, you will probably just nod your head and say, sure, okay, despite the fact that you have no direct observable reason to believe such a thing.
Radioactive decay is transmutation in the most straightforward alchemical sense.
So consider that, given the state of fourteenth century science, it was perfectly reasonable for fools and philosophers, peasants and kings to believe that iron could be turned into gold. Provided, of course, you had mastered the arcane art of alchemy. Three short answers come to mind. We can learn from the alchemist who was motivated by each of these desires. First consider the practitioner who is only interested in filthy lucre.