There are a couple of reasons I can think of - It's become a popular post (might be because it's received recent likes/comments) or because the algorithms can't find anything better to show you instead.
A few things you could try:
- Check your settings, a lot of sites have filters like "show most popular", "show most recent", "show everything", "show less posts like this" etc. You can often change how individual people/pages are displayed, but also check your overall feed settings to see how posts are being shown for you.
- Consider following more pages, e.g. other things you want to see, which will give more 'options' for the algorithm to choose from.
- Often sites will prioritise things you have interacted with in the past, for example if I like a couple of posts by one person or page, suddenly I see all their posts in my feed. You can counter this by either liking other posts elsewhere or not liking anything at all!
The algorithms really aren't great, it's basically trying to figure out what it thinks you want to see.
The most helpful posts are the ones that tell you about an event that has already passed.
