I'm one of them. I made this account for opsec reasons, don't worry I'll be careful.
This came after a 5 week strike. The contract came largely as a result of tactics such as large groups going to different regents houses at 5 a.m. and waking them up.
The lowest paid teaching assistant is moving from making about $23,000/yr now to $34,000/yr by October 2024. In Los Angeles, Berkeley, and San Francisco they'll be making $36,500.
We fucking won!
In addition to @OpsecAccount230906's answers, I will also add that there are a decent amount of professors (I don't have data, just from the UC professors I work with) that are against the wage increases because that means more grant money that they have to get/less grad students they can pay with a given amount of grants. One thing that is causing a slow moving catastrophe with academia is that grants don't keep up with inflation well. The average grant size is still similar in dollar amounts to what they were a decade ago, even though lab equipment and salaries have increased in the mean time. So, I know several professors I work with were rooting for very small wage increases so they didn't have to worry about grant money.
Additionally, tenured/expecting tenure professors are some of the most secure PMC types, so there are the obvious right wing Liberal political positions that come with that class position generally.