What do professors think about students performing poorly in his or her class?

I am curious because usually professors are either nonchalant or respond aggressively when students do not perform well.

I had two midterms recently, one of which had preparation material that was exactly opposite of the tested material (the preparation material focused on problem solving the test focused on concepts), half of the students failed. Another midterm is during that one week when every student has their year long project turned in, a lot of stress during that week and more than half students failed.

For the first one, the professor didn't even address the fact the class had a 51% average. For the second year, the professor was quite angry and said that whoever is failing needs to reconsider why they are going to school.

To us students this can appear to be extremely short sighted. This has resulted in a "difficult" atmosphere in the classroom, the professor is no longer telling jokes, the students are no longer asking questions. He knows he is not going to get professor of the year. Everyone is a bit disengaged.

But this is all from my own perspective and could be deeply mistaken given my own biases.

What do professors usually react when students are not performing well in the class? What conclusion would professor reach? And how, if anything, is done to help the students?