I don't think the buyer necessarily paid too much. I think a domain is worth what a buyer is willing to pay. When I think about dog grooming, I think it has good potential to be a winner. It's a memorable EMD that with proper development and marketing, a business behind it, could be a profitable winner. He should probably even try to trademark it.
In fact, the previous owner had a developed site on this domain for over 10 years, with the same business model as the new owner has in mind. The website 'retired' this March 2021. Only the domain has been sold in this transaction, why not the domain + website and all of the existing clients accumulated over a period of 10 years?