Comment by WCSTombs

Look, I think it's pretty hard for most of us to read long math arguments in plain text, so I wrote in the simplest language I could, leaving the simple details for the reader to fill in.

I will add that in the vast majority of mathematical literature, both in pedagogy and in research, the active participation of the reader is assumed: the reader is expected to verify the argument for themselves, and that often includes filling in the details of some simple arguments. That's exactly why math literature uses the plural first-person "we," because it's supposed to be as if the writer and reader are developing the argument together.

In contrast, listening to music can be purely passive (but doesn't need to be).