Would major car manufacturers really pay for insurance?
Yes, reason number 1 is to stop bad precedents from happening in court which could devalue all autonomous cars - and thus affect manufacturers profits. Also manufacturers wouldn't necessarily even have to have insurance because they would have enough money to cover costs. And if were legally mandated to have insurance they would have bargaining power that would halve the insurance. End result: Car companies would give you a certificate to say you're covered.
Also it doesn't make any sense for people to take on liability insurance when they obviously aren't liable for an accident because they are not driving.
note: The insurance could be split - accident liability on one hand and damage, fire and theft on the other with the damage part paid by the consumer.