Someone nominated their spouse, they are splitting and the spouse makes a fake demise post. Can legit get people to panic if the person in question is famous enough.
Also, if you are careful with your accounts (random 30 character length passwords, 2FA etc) and your nominated successor has not, that's an additional attack vector.
Personal anecdote: The LinkedIn thing happened to me. My skip level manager died in a freak accident (He was 44-45 yrs old at that time) and I noticed his profile until as recently as about a year ago. It still showed him employed at the company. I am sure people got "Congratulate <person> for completing his 5th year at <company>" while his profile was around. His profile has now been deleted. Not sure who did it or how it happened.
I would just pass a note to my relatives with my passwords and they then may delete accounts, or not. I rather care about my real life to be honest, and not my virtual legacy.
EDIT: I made this.