An obituary is not going to get shared widely or get many clicks (unless it's a celebrity), so obviously it will be ranked poorly by Facebook's algorithm. But it is Facebook's choice to rank content based on click rates and virality, so in a way they did arrange it so that post would not be seen.

"Our algorithm did it." does not absolve anyone of their responsibility in choosing to use that algorithm.

The explanation is that that kind of post doesn't provide as much "engagement" (i.e. likes, shares and in the end ad revenue) as the kind of posts that makes facebook a worse place (click-bait kind of articles, "fake news", gif memes etc).

Something like this happened to me too (though it was about a newborn baby). FB simply decided that some of my contacts are not worth showing up in my feed. Some other instead keep popping up, despite me clicking "Hide post - See fewer posts like this" like mad.

When one of the options is: "Show me the News Feed in chronological order, omitting nothing," [0] then Facebook will not be at fault.

[0] I am aware of appending /?sk=h_chr to the URL. It does not work 100%.