His kids must want to cash in on their inheritance, surprised it wasn't set up as a foundation to continue indefinitely regardless of their rapacious desires.
Good news for us is if you lusted over something in the collection you may have an opportunity to buy it in the near future.
Not surprising though. This has happened before. If the museum and collection are not the passion of the estate or inheritors, dissolution is the only solution.
Four of the most special cars are going to the Petersen Museum nearby. There was some local (LA) news on the matter in the fall. He was also planning on building another museum in Oxfordshire in UK I think; that was announced in 2018 but I don't think it ever happened.
There may be tax reasons as well for the closure. He has 6 kids and a surviving wife I believe.
I'm reminded of when the new S-Class was introduced some years back, and the MBCA offered it in their raffle. What was offered was the base model and base MSRP. Well, could you even possibly buy an S-Class with no options? I don't think so, it would have to be loaded up with a few extras probably raising the base price $20K or more. Then, you'd have to pay the tax on that "winning"...and then state tax and insurance to get the car registered.
I couldn't afford to win the prize! Similarly, if the assets of the museum were left to the seven people (or more!) who may be beneficiaries of the estate, it's possible one or more of them simply couldn't afford it without liquidation.