You make it sound like they were dangling participation in front of fans like Bulgaria, and even Bosnia to an extent does. All they said, pretty early on, was they were looking into a possibility and even that was hesitant and tenitive. Only fans were the ones who took that as conformation of participation. I don't recall them saying anything else officially until now. Everything else in between was basically from unconfirmed sources and fan sites spreading rumor.
Fans took every little unconfirmed piece of news and made it a big deal about it as they usually do. They were the overenthusiastic ones not the Turkish broadcasters. The only people laughing and think the Turkish broadcasters look like fools are those looking for a lame excuse to trash the country, which they don't deserve. There were NEVER any promises so I never understood why so many were so confident.
I might be mistaken but at the time of the first announcement, I remember that it was a definite yes. I even remember, that it found it's way in the wikipedia article as being the most early confirmation in esc history.
But as I said, I might remember that incorrectly and you are absolutely right about fans and how they react to the tiniest little bit of hint (sometimes even less than a hint).
edit: I just went through older articles on esc-today. And in the one I remembered, it was stated (from turkish officials), that "Turkey plans to participate in 2016". So I remembered it too positive, as a plan is not a "definite yes", as I falsely stated earlier. Sorry for that.
But on the other hand, "planing to return" involves not so much hesitation or mere possibility. It rather means you have made your mind up and now you try to realize it. And this sounds very differently from what they say now, because the official reason for not participating has not changed in between.
So basically the people from turkish TV are to blame (at least to some extent) for the negative image that arises now.