I was in the nether and all of the sudden two endermen started attacking me and almost killed me. If I didn't have a totem of undying I would've died. I figured I just glanced at them by accident, but then it happened again. I knew at this point it was strange because usually I know when I look at an enderman, but I was almost certain I didn't look at them. After that this happened two more times. I knew at this point that something was wrong.

I am not quite sure what is causing it, but I also noticed something else was strange. After reloading the world, the endermen didn't become deaggroed, which used to work. I am not sure whether this is related or not.

I also noticed that a few of the endermen that were attacking be were on fire. This could've happened after they became aggroed, or perhaps they took fire damage and for some reason blamed me. At that point I was near a nether fortress, so if the fire caused them to get mad at me, maybe a blaze hit them with a fireball, and caused them to blame me? (That's just speculation.)