I recently noticed that when I post old crap I'm trying to get rid of to Craigslist, I get nothing. At the same time, when I post to Facebook Marketplace things sell within 24 hours.
I started poking around a little, and noticed that probably because of this, things where I live sell for a lot less on Craigslist than they do on FB. So, I sold nearly all of my living room furniture on FB, then bought much newer/nicer stuff on Craigslist with the money.
Now I'm hunting for items to purchase on craigslist and sell on FB for profit. I imagine this will eventually even out, but seems like a good potential side hustle for the moment.