I believe what you describe is happening because Ebay have changed the procedure when a buyer makes an offer.
Once you accept the offer, the buyer has 4 days to pay - as they would with an auction.
Meanwhile, the item stays live on the site,
If somebody else makes a better offer or buys for the price on the listing, the other buyer loses out. The deal doesn't close until the original buyer has made payment.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)