Of course investigators must try to assess if crew members acted appropriately during an emergency - that's part of their job. But I think it's very easy to judge what would have been the right course of action when you are comfortably sitting on a chair with all the relevant info neatly arranged in graphs and charts before you, and you have all the time in the world to take a decision. It's different when emergency lights blink furiously all around you, controls won't respond, engines stop, people scream, you don't know what's going on and you just have a few minutes - or seconds - to react. If the captain decided for an emergency landing and it was later determined the smoke was from a trash bin fire, I guess he would have been chastised for causing a panic.