Why do people do this??

So someone accepted my offer for a candychick floss on elve. We were both finally in game and I've had all items offered correctly, nothing was replaced or anything, it was the exact offer we agreed on and exact offer THEY accepted btw. They accepted the first confirm then when it came to the last they DECLINED the trade and blocked me😭😭 I was genuinely so excited and hyped up cause I've been looking for a candyfloss everywhere and nobody's really accepting my offer,, I get my offer might've been terrible but if they didn't want it then why accept the offer in the first place, send me a friend request and confirm the trade just to decline last minute?? It's so annoying 😭💔