If you look at the Whois records for both websites. The one that takes you to Kellyco (the .COM one) was created long after Bart purchased the .NET domain name. It may well be that the bigboyshobbies.com domain was not available at the time Bart purchased bigboyshobbies.net. At one time, starting in 2005, the domain bigboyshobbies.com, was used by a company selling equipment for racing cars. Bigboyshobbies is, after all, pretty generic and could cover a wide gamut of hobbies besides metal detecting.
Sometime after the car part company closed, the domain name they were using expired and was put up for sale. For some reason, KellyCo and not Bart, decided to buy it. I don't want to debate the ethical/unethical aspects, but it happens in industry all the time.
Web search engines are supposed to list the most search web page at the top of the list when one searches for an item. As an Example Metal Detector. But the search engines can be manipulated so that a specific company will always show up first.