Well obviously there are a ton of factors that go into the outcome of a football game and the level of motivation based on the outcome of the previous the previous game is one of many. I wouldn't say it's a big enough factor where you would see an inarguable correlation, especially in the small sample size you provided but based on personal experience and human nature, I 100% believe in most cases it absolutely helps. Just like having a bye week, it definitely helps buts it's not a big enough factor where you would see some direct correlation to winning the next game. I'm sure you could provide me with 6 different examples of teams that lost coming off bye weeks, like you did yesterday, but if you did, I would still maintain that they lost in spite of those bye weeks, not because of them and it 100% helped.
Of course there are going to be some exceptions. A loss can put a team in must win mode. If OSU or Bama or Michigan lost then that would put them in must win mode to make the playoff. If an NFL team in the playoff chase had a two game cushion to make it but then lost a game resulting in the next game being a must win then that would create some urgency for them. But Fresno State is not in any of these situations. They are not in must win mode and this game is not a must win for them. And I am glad that they came back from behind, got their hopes up thinking they could win, got a huge 4th down conversion and then completely blew it. You could tell many of them were sad I don't believe that will help them at all in their next week of practice considering all the effort they put in to beat USC to come up short.