The difference between #25 and #23 is statistical noise.
The US News rankings have very little to do with the quality of undergrad education, so it is unlikely that any rise in US News rankings is due to an improvement in “quality of education” (which is pretty hard to define, let alone measure).
USC (and Northeastern) are known for putting lots of energy into improving their US News rankings. This tends to be the be the most effective way of rising in the rankings, much more effective than trying to improve the “quality of education”.
https://www.insidehighered.com/news/2009/06/08/usc
http://www.bostonmagazine.com/news/article/2014/08/26/how-northeastern-gamed-the-college-rankings/
USC does not perform well in results based rankings such as Forbes and Payscale despite having large (highly ranked) engineering and business schools, a large alumni network, and an urban location in a relatively expensive part of the country.
This does make one wonder if someone has spiked the kool-aid…