I don't think that's quite the case. Brookes is an England prop that came with high expectations, which his career to that point suggested he hadn't lived up to. Whilst he is a very good at scrum time, his efforts around the park haven't always been as good, which is probably not helped by Zhvania thinking he's a centre whenever he gets his hands on the ball.
JTA appeared to be written off pretty quickly, but has worked hard to get fit and is a popular member of the squad. One thing I noticed at the Bath match in November was how he interacted with the rest of the team. He was the only player to make sure Gaskell was comfortable and ok when he went off injured.
Another factor in why people were so pleased to see JTA come good was because of the prospect of Brookes being out for a long time.