The pair tied the knot in a $20 million ceremony in August but Kardashian filed for divorce on Monday after only 72 days of marriage.
According to People, both parties knew that the union was not working and had multiple conversations about splitting, though it was the Keeping Up with the Kardashians star who eventually made the decision to end the relationship.
"[Divorce had] been on her mind a lot lately. She was completely torn. Kim decided really last minute. It was not an easy decision to make," a source told the publication.
"[Kim] talked about the possibility of filing and she told Kris it wasn't going to work. Everything she dreamed of in her mind was right there in front of her but what she realised is that her heart wasn't there."
The insider added that the divorce filing was still a shock to NBA player Humphries, adding: "[He was] surprised by the timing. He found out about the divorce papers via the internet. He thought they were going through troubling times and a really tough situation but he thought they would figure it out."
Kardashian is said to have told family and friends that she feels "embarrassed" by the failure of her marriage.
The reality star cancelled her Australian tour earlier this week amid the split.
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