This guy is in a shit situation but when I google "World Trade Center" and "Oklahoma City", the images of the terror attacks are among the first thumbnails in the general search.
Yes, of course they were both bigger events, but not so much in relative terms. This truck explosion led to the deaths of nearly 500 people, in one of the most gruesome ways possible. His resort is just a small resort...no number of decades is going to ever obscure such a horrific catastrophe.
That said, why didn't they change the name of the place? I suppose as late as last decade, Google results were not a big factor for most resorts. But better late than never, since presumably their brand and reputation won't get much better.