Definitely some inconsistencies when you look at the big picture. They are just modelers, their heads are deep in lots of data.
My guess for the dire modeling is this - the virus stays the same, but people get more susceptible to any virus as their immune systems wane in the low vitamin D winters.
All in all, I am a glass half full guy and the modelers are definitely glass half empty. I think we’ll be below the low end of their estimate, and I have a hunch it’ll be that dastardly thing called herd immunity. Time will tell.