Wizard Malon sounded excited when he pointed out that it was a stone giant that Abel possessed. Yes, Johnson was a stone giant, but he just wasn't sure what Wizard Malon was so excited for.
Truth be told, the stone giants were technically sources of an endless supply of magic gemstones. Law-defying wizards needed these stones, so very naturally, Wizard Malon just thought that he had wandered across a walking mining pit. He considered it extremely fortunate since it was the reason he built the blizzard clan in the first place. Well, it was pretty much just for the sake of getting more resources. Now that there was no longer a need to go through all the work, there would be a whole heap more time for him to go through the other stuff.
Some readers pointed out the problem of Wizard Malon openly using his powers. While it is true that law-defying wizards aren't allowed to use their power in however ways they wanted, that rule only applies if there aren't enough things to tempt them. To begin with, the reason he never killed off the entire third squad was so that the lightning clan wouldn't become so desperate to hunt him down. The cost of making a move was already too great, given how he's already thought about leaving the Blizzard clan as soon as he did so.