UAW set it up so that the entire UC system votes on these contracts. This leads to situations where you have large student protests at union meetings followed by students at other campuses voting to ratify the contract, and then entire campuses holding unauthorized strikes in protest of the contract they just "voted for".

If things were department wide, or even campus wide, the UAW wouldn't last a year in the departments I'm familiar with.

Instead, what you're proposing would require a statewide campaign against one of the most powerful political groups in California. The UAW is well aware of this, and has no incentive to act in its members' interest.