gap insurance protects the lender in the event the borrower cannot meet the terms of the lease, it's only sold under the guise of protecting the borrower, it's an insurance premium. if the borrower can meet the terms and the vehicle is a total loss, the vehicle insurance will close the lease or replace with a new vehicle (if available and under the terms of the policy) which the lender can then "swap" into the existing lease
as for "not a thing" I replaced a Porsche and the lessor wrote an asset swap. It avoided some fees to terminate and start a new lease. That's how I know it is a thing. : )
Of course most people without experience in business, especially trading, don't make sense of it, and only people with experience in leasing tend to learn the "wow" of leasing a vehicle (in my case, a GT3 RS) that was worth a multiple of its cost basis after I'd driven it for two seasons) and the "thankfulness" of having a Range Rover and a Tesla both deep under water and happy to walk away from the lease.