Why is the AI so aggressive in vanilla?

Okay, so here's my situation. I was going for a Science Victory on King and I got it. But all throughout the game, the AI does nothing but declare war on me. I mean, since I was much further in technology, I could handle them; but still, I haven't attacked anyone or anything and the AI is declaring war.

Also, does the AI understand when it sucks? I don't think it does.

For instance, I had Industrial units and Elizabeth is still using Renaissance units. Yet, Elizabeth is talking trash and denouncing me like she's the most powerful empire. Then she declares war on me only to get painfully defeated. Then she asks for a peace treaty, then 50 turns later, it's the same thing rinse and repeat.

I've also noticed that, the AI doesn't seem to get a DoW even when playing super aggressively.

For instance, after I got my Science victory I decided to do a little epilogue play. Suleiman is playing super aggressive, yet none of the AI are declaring war on him. So, I decide to go in and liberate the city state he's attacking. What happens next? WORLD DOW. It's BS how the AI can be super aggressive and not get a DoW, yet I haven't attacked anyone and I get a WORLD DOW.

Vanilla is a mess and it is widely known as such. G&K was a HUGE upgrade and BNW is even more so. I recommend investing in the expansions. The AI still has some quirks (in BNW it's actually not aggressive enough! XD) though much of the frustrating senseless hate is gone or more transparent.

ya the expansions saved the game for me basicly Civ 4 was my favourite before BNW came out. Its like a whole new game

AI is actually even more aggressive in G&K than vanilla. (Since the Fall G&K patch greatly increased AI cash buying of units). But G&K did stop most of the insane DOWs where even the AI thought it was going to lose.

It's BNW that has it about where it ought to be.

Vanilla AI almost always went all or nothing when you started taking the lead.i.e. if it wasn't winning it would just DoW you in the vague hope it would actually beat you because it had no other way to do so.

As mentioned G&K AI was more aggressive but it was generally logically more aggressive. It would DoW you because it was bigger and technically better than you and on paper it should win. So it would DoW because it thought it could actually win not because it was victory or death!