because there is no requirement for passing a math test to get into Berkley. US higher ed has no entrance exams.
students got passing grades in math coursework, sure, but that does mean they know how to do math, because schools don't teach it. same with reading and writing.
high schools and education in general, is all about passing as many people as possible, it's not about rigorous educational standards and sorting.
many students come from educational systems of varying quality, some of which were rigorous, some of which were not. and they won't know that until they get their ass kicked in higher education.
and the administrators solution is to lower standards, because that's easier than having kids do remedial work.
I got into Harvard. I got my ass kicked, because I was from a poor school and underprepared. I managed to work my way up from a C student freshman year, to a A student by Junior year. I had to re-learn grammar, algebra, and reading skills, but I was able to do it. Just because kids don't know it coming in doesn't mean they are not capable of learning it and succeeding.
In my high school I was like top of my class and had 3.8 GPA. And freshman year while I was struggling and working my ass off to get Cs, there were people who barely worked who got As, because they had gone to elite private schools and had been taking college-level coursework for years already, who already had not only academic knowledge, but all the social elite entitlement, if they got anything less than an A they'd harass their professors to bump their grade, and I was terrified to even go to office hours to ask for basic help.
A lot of students are also just entitled lazy assholes who refuse to learn and blame the professor/teacher.