Just a thought or three here about how EVs can drastically cut down CO2 emissions indirectly
There's three fronts of "attack" that EVs can lower emissions
Decreased number of oil refineries and refinery products.
Gasoline and diesel make the lion's share of profits from oil refineries. Oil refineries also make other precursor chemicals for polymers
In order for the refineries to exist and be profitable, they have to switch to making other products, such as plastics, waxes, asphalt tar, and even carbon dioxide for that matter. Refineries still have to make a profit so they will increase the price of the "other products" to maintain the profit.
Increasing those prices makes plant/renewable based polymers more economically feasible (locking CO2 in place).
Making the grid more predictable and level.
Currently most EV owners charge during "off-peak" hours which means they are using more nuclear energy in the mix (at least in the US). Having a leveled off grid usage allows engineers to design a grid with a minimal amount of peak demand. This allows more of the grid to be nuclear and hydroelectric. Currently hydroelectric is used for peak usage, but if there are no peaks, it can be used for baseline generation. This also means that the equipment does not have to be over sized so it can operate at peak efficiency
Old EV batteries are cheap energy storage for wind and solar energy
Currently, at least from my understanding, wind energy fluctuates and needs buffers to ensure a stable amount of energy to be input into the grid. Solar only works when there is sunlight. This is mainly handled by lead acid batteries which are costly and do not have a long lifespan. Old EV batteries could provide wind and solar energy with a cheaper alternative in order to release the energy as needed. The costs of wind and solar are decreasing (due to old EV storage batteries), while the price of coal and natural gas increase.