Take a look at the 20-24 and 15-19 age groups. Note that 15-19 is smaller, and consider that members of that age group will move up to the next group over the next 5 years. They're also entering typical college age. Now, in this chart, it's far from a "cliff", but it is smaller, so that would mean that you could reasonably expect a lower enrollment since that age bracket is smaller than those that came before it.

Some schools are more effected by these demographic issues than others. Institutions that are focused on educating lots of people economically, like CSU, can be expected to feel the demographic swings far more than places like Stanford or Berkeley which are over-subscribed and are likely to remain so.

Presumably, the school was built / staffed for a certain regular enrollment that reflected some percentage of the people in state.

For California specifically:

https://data.census.gov/profile/California?g=040XX00US06

You can see the peak of 25-30 somethings, and then it drops off.

When you start looking out at the 15-19s there are 400,000 fewer than the 25-29s (roughly 3M -> 2.6M). That then means that enrollment is going to drop and things will need to be cut.

The school that I went to for grade school was built for baby boomers. It was large, and the next town over likewise had a large school. When I went it was a bit empty, not too bad though. It picked up again with the echo.

The towns have recently closed half of each school and combined classes because there isn't enough students to keep two sets of classes running at reasonable funding levels (having a class of five 3rd graders and six 4th graders is great for student to teacher ratios ... not so much the budget of a small rural school).

Suspect this and a tight labor market are the two driving factors.