So what in the heck happened to make Rory McIlroy dump his bride-to-be Caroline Wozniacki . . . and promptly win his first tourney since 2012 with a thrilling win in the BMW PGA Championship in England on Sunday?

According to Monday’s Belfast Telegraph, local hero Rory was petrified that his tennis playing sweetie was turning into a "bridezilla," so he decided to pull the plug before things really got out of control.

The sporting world’s golden couple got engaged at the start of 2014, and Caro was eager to make it legal sooner rather than later, with wedding save the date cards sent out for a November party in New York.

“He really didn’t expect wedding plans to take shape so quickly but Caroline just got totally carried away — he thought they wouldn’t get married for years but she became a bridezilla,” a McIlroy source told the Telegraph.

“He found himself in the middle of something he couldn’t handle, a wedding planned less than a year after they got engaged, and when the invites went out that was the last straw, he freaked out.”

The engagement took many in McIlroy’s inner circle by surprise, the pal said.

“Things haven’t been right between Rory and Caroline for about a year now, he’s made that very clear,” said the friend.

“Everyone was completely shocked when he proposed, but he thought that would buy him more time because Caroline had made it clear she expected him to pop the question. It’s a weight off his shoulders now. He wants to focus on golf.”

Will heartbreak suit Caroline’s career pursuits as well as it has for Rory so far?  She’s already lost in the first round of the French Open this week, so we’ll see. 

She hasn’t commented on the split other than to thank fans for support on her Twitter feed.  She’s also cheering herself up by keeping company with her pal Serena Williams in Paris.