Why was Satan so small?

In an effort to think about anything what the actual crappy end to our favorite characters, I’m thinking about Satan. Toby Jones is a great actor, but why him for Satan? I’m sure Benedict would have been up for a cameo. But I think picking a small older man was purposeful. Without humans, what is Satan exactly? Sort of nothing. A diminished ex-angel with no one to tempt, no souls to gather, no demons left. That was sort of elegant. And I’m sure if they hadn’t been in a ridiculous rush, that would have been explored. Also he seems less evil and more…regretful, that this is how everything turned out.