It doesn’t matter about the championship team; research confirms that most of them had a close call during their season of glory. In the last 20 years, half of the teams which became national champions lost one game.
In 2007, LSU won the title, but lost two games, which is very unusual.
Dating back, when the polls were used to determine the national champions, there were some regional influences that affected the final vote. There were multiple champions by different polls in a given season. Then came the BCS format which segued into what we have today.