According to https://edd.ca.gov/Unemployment/Eligibility.htm in order to qualify for unemployment benefits in California, you must be "physically able to work, available for work, and ready and willing to accept work immediately"--obviously that can't be the case if you're incarcerated.

In the recent cycle of articles about CA unemployment fraud, it's been widely reported that inmates involved (not necessarily perpetrating, some just had their names used) in this fraud were from all around the country.