Or maybe they were involved and confessed during questioning for a bargain? Just because they did not tell things you wanted to hear doesn't mean they were given under duress or torture.
In any legal system that deserves to be called legal, sole confession without other strong material evidence is not acceptable.
Bargain, sure... No beating, no electro-shocks, no sleep deprivation. They just ask politely and show a little friendliness. Right.
If they have material evidence, what's the use of a "confession"? If they don't, there's something fishy already.
BTW, there obviously WAS some sort of coup or "coup". But who pulled the strings, what were the intentions, and, most importantly, were all those tens and hundreds of thousands people involved is completely fishy, judging by the news, and especially official news from Turkey.
I understand the skepticism, this is my personal observation so far. I read the initial statements, in time there will be court proceedings, and more data. They seem quite genuine to me. Unfortunately they are mostly in Turkish.