Because society is sick. Divorce is an enemy not a friend, it's not the convenient way out people pretend it is.
No, society was sick. That is why people were forced to stay together and live in misery. We still have depraved people who'd like to go back to forcing others to live in misery.
Also while divorce can be hard on children anyone who thinks it is better for children grow up in a home where the adults fight with each other day and night, clearly loathing each other, needs their head examined.
Then why is it that people live their most optimal lives in this "artificial thing"?
This confuses two separate things. Yes, there is a demonstrable benefit to living in a happy, stable relationship. But that relationship does not have to be permanent. If someone's happiness instead derived from knowing that the person they're with can't leave then they're a sick individual.