This is certainly nothing new and not limited to cults. Salesmen use the obits, wedding license notices, new home sales documents, etc. to contact prospective clients to sell them their products.
If a young couple applied for a marriage license they might be contacted about buying a life insurance policy or stocks to protect their future.
If someone purchased a new home a salesman would contact them about homeowners and car insurance.
They could contact a recent widow about covering their cars mechanical and electrical systems as their husband handled all this prebiously.
You could say the sales person was contacting them at a vulnerable time, but if the widows transmission went out next week, she would be thankful for the coverage.
It seems to me the Corps studied the book, “How To Win Friend and Influence People,” and adopted it’s principles to their goals of winning folks to the class.
Good ideas will always be used for bad outcomes.