Fitzpatrick won the 2013 U.S. Amateur on the same course, so he had some fan backing but not a lot. He had won seven times on the European Tour but never on the PGA Tour coming into the Open, though he had been in contention numerous times. Overall he was known as an excellent player but certainly wasn't a fan favorite or expected to be one of the main contenders to win. I know I wasn't rooting for him, in part because he had shown almost no personality on the course, but once he accomplished his well-earned feat he and his large number of family and friends present showed sheer unrestrained joy. He smiled non-stop and was witty and engaging, and coming from a working class background in Sheffield made it that much easier to like him and what he pulled off.
Fitzpatrick also noticeably increased his length off the tee without bulking up, which I like to see. Players like Fitzpatrick, Will Zalatoris and Justin Thomas are able to effortlessly pound long drives without looking like easily injured hulking linebackers (Koepke) or defensive tackles (DeChambeau). There's no need for golfers to look like they're prepping for Strongest Man contests.