2. Jim Harbaugh's offenses in the NFL are very good
During the 2011-2013 seasons as head coach of the San Francisco 49ers, Jim Harbaugh's offenses had the 11th-ranked scoring units. They also had the 8th, 4th, and 3rd-best rushing attacks. Well, for the Denver Broncos, they could not stop the run in 2023, and in fact had the second-worst run defense in the NFL.
Furthermore, Justin Herbert has proven to be a passer that can carve up defenses. Even with limited regular season success. Herbert has still thrown for a ton of yards and touchdowns. I think what Jim Harbaugh is wanting to do is to not only field an elite rushing attack, but also field an elite passing game.
He appears to have the QB to be able to do that, and Harbaugh's rushing offenses are very good, and they have been that way for years. The Chargers, all of a sudden, might have a balanced and elite offense. The Denver Broncos would have their hands full on defense, and even with the unit playing well down the stretch, it was still, largely, a below-average one.
The Chargers will be even tougher to beat if the Broncos themselves cannot field a competent offense.