Was Fletcher purposely sabotaging his own performance at the end

Obviously we know why he does it, but out of context it's a little odd... say he got his revenge on Andrew and humiliated him, the what? The night was still ruined and the already disgraced music professor now looks like a complete joke who can't even handle a JV band. Were his designs for revenge really that much that he'd sabotage everyone including himself? I guess the answer is yes, he's a psychopath, but still...

I'm also unclear how he goes from being fired from Schaeffer, to conducting in Carnegie Hall. This seems like an undeserved upgrade, or failing upwards, rather than a fall from grace.