I don't for my opinion. I think every villain from the game just have reasons to do what they do.

I forgot about Gaius I'm sorry
Nidhogg wish to get revenge over humanity
Yotsuyu hate her people and wish to dominate them because of her sad past
Zenos wish to face a worthy opponent (remind me a little of Lu Bu in dynasty warriors by moment)

As for the ascient... They are just like "hey people! We're going to make shit so you can shit on us be cause we are shitty guys!"