I think that you will have to pick a particular topic or aspect of a topic upon which to base your expository essay. Since most of it is informational, based on evidence or analysis that you can find or assert, I think you have to select some aspect of a point of view to defend and explain. It is not like a persuasive essay, but to a great extent, your purpose in an expository essay is going to be writing about information, aspects of it, and defending it with your analysis and the evidence that you find in a text. This is what makes the selection of a point of view critical. Another way to think of this is with the idea of a thesis statement. Your thesis statement, or what you are going to prove, has a specific point of view. This is something that is understood and the point of view in the thesis is what will be demonstrated over the course of the writing. In this light, one sees that a particular point of view is critical in writing. It is the nature of the expository essay to have a definite point of view from which evidence and analysis can be posited in convincing the reader of an informed and informational mode of written presentation.