As for copyright - I doubt many people care. Why should her relatives gain from the photography when it was the work of others that made it valuable? In this instance, what the photographer provided was raw material. It was selected, printed, and promoted by others. Her relatives had nothing at all to do with it. Perhaps legally, they deserve a significant percentage. Morally, however, they deserve none.
Either copyright has value, or it doesn't. It amazes me when I see photographers discounting the value of copyright.
There are mechanisms in place to deal with intestacies. They are often awkward and slow, but they do reflect a societal value that says something like: if someone dies without close relatives and without a Will, it should
not be either the government or those who seek to profit from the deceased who get their hands on those things of value that belonged to the deceased at the time of her death.
And if the issues had been dealt with appropriately, which admittedly would not have been easy, there would have been ample opportunity for Mr. Maloof and the others to have profited well for their efforts. They certainly owned the negatives and prints and movies themselves, and those items were necessary in order to harvest the value they did.
I truly wouldn't care if Maloof and the others received almost all of those profits - that is often the case with publishable and distributable art.
And by the way, it isn't clear to me that it would have been all that difficult to find Ms. Maier while she was alive. There certainly were a number of her former charges who were still engaged with her prior to her death.