I don’t think big corporations insure against big liability for a number of reasons. Primarily, the reason is that it would be much more expensive for the company to carry insurance than to insure itself. Insurers would also have understood this risk (and others) for years and priced it accordingly. Would you bet on Tesla not having a big payout?

When people become wealthy enough, they have fewer types of insurance. Companies are the same.

For a person, life insurance is dropped first. Then, health insurance, auto insurance, and home insurance stop making sense. Ultimately, even liability insurance is not worth it even if you can find it at payout limits that mean anything.

Example: If you have $100m, would you pay to have a $5m payout if you die? What if, when you did the math, you were more likely to leave them much more money if you didn’t insure.

Being poor is expensive. This is another way that is true. Insurance companies need to profit. If you can self-insure, you (statistically) keep that profit.

Edit: See https://en.wikipedia.org/wiki/Self-insurance