Scores of articles on Google News refer to Wimbeldon.
How did Mr. Rewrite confirm the spelling? By looking at the official site, www.wimbledon.org.
Back in the day, Mr. Rewrite would have to check clipping files and reference books to confirm the spelling. Fact-checking is too easy these days for this proper noun error to be so widespread.
Perhaps this grousing is misplaced anxiety. Roger Federer is down two sets to one and playing for his life in the fourth.