Actually, my sources for my post were Not Since Carrie: Forty Years of Broadway Musical Flops by Ken Mandelbaum, and The Happiest Corpse I've Ever Seen by Ethan Mordden. Those, undoubtedly, were based on interviews with her as well as knowledge of both productions.
I will agree that Betty Buckley was a perfect fit for the role, and a far better choice than Barbara Cook. However, I feel like Barbara Cook's performance
on the Stratford archival video, specifically, was phoned in. Barbara Cook could do better, had done better before, and has done better since. Whether or not it was a personal choice to
"decide we are not gonna play the role to the best of our ability coz we dont like the show as we are been paid to do a job(it also doesnt look good personnaly" is beside the point. It is entirely possible that at that point in the proceedings, the "phoned-in" performance WAS the best thing she was capable of in the present situation, personal choice notwithstanding.
And no one grew into anything new, we just became the worst of what we were."