This is all about wealth redistribution and socialism/communism which dominates California politics.
The largely socialist/communist California assembly understands demographics well; and they understand that the bulk of this commie tax will come from the generally more conservative suburbs. And that a good part of this money will go to their supporters (and not roads).
It’s the same motivation for charging light pickup truck drivers a huge yearly surcharge/tax/fee just because they drive a pickup. Most of these assembly members understand that the majority of their supporters don’t drive pickup trucks.
We already pay enough taxes in California – start rolling back the outrageous pay/benefits for govt workers and California will have more than enough money to maintain roads.