Given how Borg ruled Wimbledon at the time, and even more so following his crushing win over Connors in the semis, an easy, one sided win for him in the final was widely expected. Yes he had a huge scare vs. Amritraj in the 2nd round, but early round scares at Wimbledon (vs. Edmondson in 1977 and Amaya in 1978) were common for him, before he noticeably improved and looked a lot more assured during the business end of the tournament. I think there were pre-match odds of 1/7 in the UK for Borg to win, which highlights that.
So the fact that we instead got a 5 setter, was a very pleasant surprise.
Tanner serve-volleyed behind almost all of his 2nd serves, and also frequently charged in on Borg's serve, as threw all that he could at him. Borg admitted that when he served for the match in the final set, and saw 3 championship points come and go from 40-0 up to deuce, he was incredibly nervous.