Remus Lupin was the only good professor for Defense Against the Dark Arts
Defense Against the Dark Arts is a cursed position at Hogwarts but Remus Lupin was the best teacher they ever had and probably the only good professor to take it on.
Why Severus Snape wanted to be the professor of Defense Against the Dark Arts is something that never made any sense because it is a cursed position at Hogwarts BUT, that being said, let’s take a look at the best professor to take the job: Remus Lupin.
Yes, Remus joined the school for two reasons outside of actually teaching. He knew that Dumbledore would hire him despite being a werewolf and he also knew that he could help protect Sirius if he was there. Both of these drove him to go to the school but it also made for the best teacher Harry had in Defense Against the Dark Arts.
Most everyone who taught the class either wanted glory for themselves or were doing it because it got them close to the students. Remus had those reasons but he also was just good at it. He found ways of teaching the students what actually could harm them and he spent the time to explain what was the best way of protecting themselves. Sure, Mad-Eye Moody probably COULD have been a great teacher for Defense Against the Dark Arts but he also never got to actually teach the class because of Barty Crouch Jr.. Instead, we just really have Remus Lupin.
He was the only one who made sense in the role and the only one who actually taught the children something and that’s why we love him so much.