You insure yourself, not the other drivers.

It's analogous to buying flood insurance. It's super expensive because the only people who buy it are those who live on floodplains.

If the only people who bought car insurance are the riskiest drivers who are clinging to less safe forms of transport, and the rest of the pool that used to contribute premiums are now in safer, cheaper autonomous vehicles and different forms of insurance, then the manual group would need higher premiums.