1. The LA Chargers have more motivation
Sometimes it is as simple as being the more motivated team. In this case, the Chargers just have more to lose and more to gain.
LA is sitting in an uncomfortable second place in the AFC West after Week 8 jostled things around a bit. At 4-3, the Bolts are barely edging past the 4-4 Chiefs and Broncos in the standings. A win could put them back in a shared first place, and loss could potentially push them towards the bottom of the division depending on how the other AFC West games pan out in Week 9. For a team that started 4-1, dropping such an important game to the 3-5 Eagles is unlikely.
And the motivation isn't as microscopic as divisional standings in the middle of the season. When it comes to the bigger postseason picture, LA is occupying the last slot in the current playoff standings. Simply put, there are a lot of mediocre teams in the AFC this year. Or at least teams with mediocre records.
For the Chargers to distance themselves from that group, they can't afford to lose such a winnable game. Every week is going to shift this playoff picture and LA needs this win to propel them into a more secure position with some interesting tests in the weeks ahead.
In contrast, the Eagles are a ways behind the 6-1 Dallas Cowboys in their own division. They are also four spots back from entering the playoff picture and wouldn't gain much better positioning with a win against LA.
At the end of the day, this better coach, more talented Chargers team has all the motivation to put the pieces together and leave Philadelphia with a win.