I imagine most of it has to do with college readiness level. The rigor is roughly the same across all of these schools but since there are weaker students at CSULA vs Cal Poly, fewer students end up graduating on time or at all.
San Jose has more engineering/CS majors than San Diego which is why their rates are a bit lower.
I wouldn’t read too much into graduation rates though as they are more indicative of student preparation than academic quality. If your stats are much higher than the average for any given school, your chance of graduating on time are much higher than what the numbers would suggest.