Can someone explain this to me please

[Doodlrodz]

I have also had this happen a couple of times lately, told the guy I would take the item and even made arrangements to have it picked up and he emails me later and says no longer available. So I look back at the ad and I see a guy says pm sent and remember his user name, he had tried to snipe me before, jumping in after the deal and offering more money. All I can say is if you're selling to the highest bidder there's a site for that and it's full of scum bag snipers.