its not a stupid question, it is just asked a lot. The lines came into captivity in different ways. The few butter lines were imported like most morphs. Lesser however was a little more interesting. A platinum was imported, which we now know is a combo with the daddy gene and lesser, but when it was imported, we had no idea. RDR called it his platty daddy. The first breedings produced animals that did not look like the platinum, but were still different. They were called lesser platinums (which is now shortened to lesser). The daddy gene is very difficult to tell without the lesser gene, so it took years before it was finally figured out you could pair a lesser with a daddy gene and make the original imported animal, the platinum.
While it is pretty obvious now that lesser and butter are the same morph, back when people were trying to figure out what was going on with the lessers, it wasn't as obvious. Now we have plenty of examples, platty daddys and butter daddys and all sorts of evidence to show for it.