So, the Endermen were staring at the dragon   sometimes, and they attacked the dragon, following it around, and the glitch gathered a whole crowd.

how to do the glitch: go to the end, and make the Endermen look at the dragon.They should follow it around until they die. Also, you can place beds on one block. And water can flow through blocks if it is on a roof, or if you place lava then water, or water then lava. (It is a random chance.)