Well, I kinda did in my last paragraph. But if you want it more ELI5:
"Some molecule shapes rotate like windmills when light or radio waves (same thing) pass close by them. Water happens to be one of those shapes, but there are others in food too, so it is not just about water. Also, there is nothing special about the frequency of microwaves to make this happen; microwave ovens use that frequency because it is considered a "free for all", and you don't have to ask the government for permission to use it for anything (cooking, bluetooth, or otherwise.) The frequency used for the microwaves does make some sense for use in a microwave oven, because that frequency tends to penetrate deeper into food than visible light does."
That's still a model -- because everything is, the map is not the territory -- but it's close enough that I think most internet pedants won't try to refine it more.
... because shortening isn't butter. Someone else in this thread mentioned that fats have dipole moments, but that doesn't mean that all fats react with the same intensity. For any affected substance: molecular weights, crystalline structures, etc all play a role.
You aren't uniquely "ringing water's bell" with 2.45GHz
"Some molecule shapes rotate like windmills when light or radio waves (same thing) pass close by them. Water happens to be one of those shapes, but there are others in food too, so it is not just about water. Also, there is nothing special about the frequency of microwaves to make this happen; microwave ovens use that frequency because it is considered a "free for all", and you don't have to ask the government for permission to use it for anything (cooking, bluetooth, or otherwise.) The frequency used for the microwaves does make some sense for use in a microwave oven, because that frequency tends to penetrate deeper into food than visible light does."
That's still a model -- because everything is, the map is not the territory -- but it's close enough that I think most internet pedants won't try to refine it more.