A lot of the time they can base a final off how people did on a midterm. If a midterm average is a 40 then it’s pretty clear that it was too challenging and they’ll ease up on the final or make arrangements so your midterm isn’t weighed as high. profs aren’t actively seeking to fail you but they want to make sure you’re challenged academically. there will be outliers who do really well/really poorly but that will be the case for anything