The fans reactions aren't based on chances, or goals really. De Vries was a very frustrating player, he wasted a lot of good chances by hesitating or trying to be to clever and turn when he didn't need to. He also was expected to be good in the air, and this was frustrating, although i blame the other players for this aspect, because they persisted in hoofing it to him.
Also i think because, De Vries did prove at times that he was quite skillful, and could be strong, but most of the time failed to live up to those standards. when you know somebody is capable of better and they consistantly under perform that is frustrating.
Connolly's scoring record to start with was poor, but he tried every game, and showed the same ability to create chances and a willingness to keep trying even when things weren't going well, so the fans stuck by him.
Hume is similar, you know given time and a bit more confidence in front of goal he has the ability, and the attitude to be a really good player.