From the article: ‘Pompeii director Massimo Osanna said the animal was a thoroughbred likely used for races, not farm work.’
The horse was a time traveler. The thoroughbred horse breed wasn’t developed until the eighteenth century:
‘It wasn’t until the three stallions that make up the foundation sires of the breed arrived in England around the beginning of the 18th century that the Thoroughbred breed was born.’
https://animals.howstuffworks.com/mammals/thoroughbred-horse1.htm
Right, the breed was developed in England. A cross between Arabian stallions and sturdy English mares.