California is considered to be a more difficult bat exam that other states because it has a notoriously low passage rate. Note, there are some caveats to that because California is the only state where ANYONE can take the exam, JD or no, so that obviously has a depressive effect on pass rates. Moreover, you are less likely to pass all bar exams the more you retake and the global pass rates for the exam don’t factor in retakers, so it’s a weird stat that is not as informative as a lot of people make it.
Nevertheless, bar exams (and really almost all exams in law school) are curved. It isn’t targeting a 50/50 rate, I believe, but the stat you’re looking at is total pass rate per exam versus pass rate for first time test takers. You get many repeats per exam.