Endermen began swarming directly wherever the ender dragon was flying. When he came to land on the Bedrock exit portal they were getting in my way i kept accidentally hitting them. just to make sure it was a bug i left and re-entered the end multiple times with the same result. Not sure if this is intentional but this definitely didn't happen in 1.15.2 as i fought the Enderdragon last week and this didn't happen.