Where did I go wrong?

So turn 250 I had 2 countries declare war on me, then a few turns later a 3rd one joined in. I am doing these videos for a YouTube channel, and hopefully you guys can help me fix my problem to things like this don't happen in the future. I'll leave a link below to the part where all hell breaks loose.

http://www.youtube.com/watch?v=vRbDXzTJ4yE

Never ever wipe a civ off the map unless you are ready to wipe every civ off the map.

Also, I never saw you hover over an AI to see why they do not like you. You need to play the diplo game, so you need to know what they are thinking.

Lastly, on King you should never have tech parity with the AI. At turn 250ish, you should be at least 1 full era if not 2 full eras ahead by T250.

Do you normally play and win at King games? If not you might consider stepping down one difficulty for the let's plays, since you can't take as much time to analyze without boring your audience. I know I always play a notch worse while the camera is rolling.