See this is how an electric oven works: Preheat means heat both the top and bottom elements. Bake is just the bottom elements.
I have learned how darn important it is to switch from preheat to bake when you put the item in the oven.
Our carefully over-managed Thanksgiving morning project plan had every step in the world on it -when to mix, when to bake, when to carve. But there was no task and no slack for dealing with broccoli casserole with actual raging flames coming from the potato chip topping too close to the still-on-preheat burner!
All’s well that ends well, but please heed the lessons from this!