For a team that was as ridiculously accomplished offensively as Ohio State was in 2018 (7th in points per game, 2nd in yards per game), the Buckeyes were weirdly kind of garbage when it came to converting in the red zone. They scored points 75.8% of the time, which put them snugly at 121st in the country. It should be pointed out that there 130 total teams in the FBS.
Some of those woes can probably be blamed on a season-long struggle with managing the running game. Ohio State ran for over 200 yards only four times the entire season, and their yards per carry hovered somewhere around "why do we even bother" and "Oh God make it stop." Simply put, the easiest way to convert short yardage situations is in the running game, and the most effective place to convert short yardage situations is in the red zone.
If you can't do A, you won't get B, which won't lead to C.
Before tonight, Ohio State was perfect scoring points in red zone situations only once all year, which was against Rutgers a dog's age ago. In some cases, this was a knife's edge situation where it was absolutely paramount that the Buckeyes score when and how they did. They needed every point possible to beat Maryland, one fewer conversion against Nebraska could've meant a loss, and going 0-2 instead of 1-2 against Penn State would've cost them the game.
Ohio State wasn't razor-sharp against Washington all night, but they made it count when they had to. Four red zone trips netted four touchdowns, which, in addition to being perfect in terms of scoring points, was the only time that the Buckeyes were also perfect in scoring touchdowns in their red zone opportunities all year (twice in 2018 they had actually been prevented from scoring touchdowns in all of their red zone opportunities; it happened in back-to-back games, against Minnesota and Purdue).
As Ohio State and the game tightened up in the second half, the Buckeyes were protected by red zone perfection. The end result was a send-off victory for Urban Meyer and a Rose Bowl that we won't forget for a long, long time.