Mariah Carey Divorced Nick Cannon For This???

Mariah Carey's timing is worse than a Jewish dance troupe's ... her divorce from Nick Cannon became final after years of waiting ... just days before her relationship with James Packer exploded.

TMZ broke the story, Mariah was trying for more than a year to get Nick off the dime and sign divorce papers. She's wanted to get married to billionaire James Packer for months, but the divorce made it a non-starter.

We've learned at the end of the summer, right before Mariah and James boarded a yacht in Greece, Nick signed the docs and the divorce was a done deal, clearing the way for a wedding day. That plan was shattered onboard the boat, when James allegedly had a bad incident with Mariah's assistant.

As for the divorce, we're told Nick and Mariah agreed on joint custody of their 5-year-old twins. Neither gets child support.

We're also told the prenup made a property settlement easy ... she gets what she earned during the marriage, and he keeps what he earned.