"""The Thompson/Shellys are good people--they loved Daniel and he loved them"""
From the Thompson/Shelly interviews and other videos, I get the impression that they earned their fortune, "the old fashioned way". Their wealth also propelled them into social circles they were ill-prepared to handle; especially ANS' volatile personality, problems and her "new" friends.
If someone is bleeding, you can help them. If someone is mentally unstable, it is much harder to help - you don't know where the pain is, much less understand it.
I think you nailed it. The Thompson/Shelleys didn't know what to do with her.