Itoje made 15 tackles in the final, the most in the match alongside South African Franco Mostert, but he accidentally concussed teammate Kyle Sinckler in just the second minute which was an early blow for England.
'It just happens sometimes'
A week after delivering quite possibly the greatest win in its rugby history over the All Blacks in the semifinals, England barely laid a glove on the Springboks.
"You can have the most investigative debrief of your game and you still don't know what was wrong," England coach Eddie Jones said. "It just happens sometimes. It's not a good day for it to happen."
The final stats told the story. England gained just 173 meters the whole match, less than half of South Africa's total. Praised for their discipline throughout the tournament, England conceded 10 penalties.
Jones, for the second time after Australia lost to England in 2003, failed to get his team over the line in a World Cup final.
"We're the second best team in the world," he said. "We didn't meet our goal — our goal was to be the best team in the world, and we're the second best team in the world. So that's how we should be remembered.
"I think the players prepared tremendously well for this World Cup and played with a lot of pride, passion and we got caught short today. Why we came up short today I'm not sure and sometimes you never know."
"The only thing I'm worried about now," Jones said, "is having a few beers. And after we have a few beers today, we'll probably have a few more beers tomorrow. And then probably Monday. And then maybe we have to pull up stumps."