a (glee) thought:
Revelation: The Troubletones' departure isn't out of jealousy: it's the disillusionment of Mr. Schue. They don't trust him to play fair and to ever showcase their talents. And why should they? He's never really been fair to begin with. Mercedes is one of the best singers in Glee, and yet she had to leave and join the Troubletones before she got a competition solo.
After all, Rachel, for all her barking, doesn't choose who sings at Sectionals/Regionals/Nationals. Mr. Schue does. And for all of his talk about diversity and how we're all in this together, he always, always always, puts his best out when the stakes are at the highest (Regionals/Nationals). In years past, that's been Finn and Rachel, but now that Blaine's there, they know it's going to be the "Blaine and Rachel show". It's also why Finn gets so jealous: he knows with Blaine's talent, he's never going to sing the lead again, at least not with Mr. Schue's choosing. Mr. Schue has absolutely no faith in anyone who isn't Rachel Berry, so in return, the kids have no faith in him.
(Which really isn't very fair to Blaine because hey, he just got there, he doesn't demand solos like Rachel, and he really only wants to see the group win and make friends.)
tl;dr: the kids have no more faith in Mr. Schue, if they ever had any to begin with.
After all, Rachel, for all her barking, doesn't choose who sings at Sectionals/Regionals/Nationals. Mr. Schue does. And for all of his talk about diversity and how we're all in this together, he always, always always, puts his best out when the stakes are at the highest (Regionals/Nationals). In years past, that's been Finn and Rachel, but now that Blaine's there, they know it's going to be the "Blaine and Rachel show". It's also why Finn gets so jealous: he knows with Blaine's talent, he's never going to sing the lead again, at least not with Mr. Schue's choosing. Mr. Schue has absolutely no faith in anyone who isn't Rachel Berry, so in return, the kids have no faith in him.
(Which really isn't very fair to Blaine because hey, he just got there, he doesn't demand solos like Rachel, and he really only wants to see the group win and make friends.)
tl;dr: the kids have no more faith in Mr. Schue, if they ever had any to begin with.