I don’t suppose that it has anything to do with the proliferation of all-you-can-eat sand bars stocked with seals? I grew up in Chatham on Cape Cod. From 1950 on, seals were unheard of except maybe in Provincetown (harbor seals). Sharks or various types were present in some abundance. Now, you can drive a boat the length of Pleasant Bay and see hundreds if not thousands of seals. And seals are a sharks favorite entree. Ergo, its not the water temperature that’s attracting sharks of all kinds. It’s what’s on the menu.
They never mention the seals. Kill the seals and the sharks disappear.