Therapeutic surgical removal of the thyroid gland

Therapeutic surgical removal of the thyroid gland was documented more than 1000 years ago. In the 19th century, a surgeon performing that procedure had only about 50% patient survival, and patient death was often unrelated to nonspecific complications such as infection or bleeding. What condition of the thyroid is so easily diagnosed that ancient surgeons would think to remove it? What hormonal problem unrelated to thyroid hormones may account for the 50% mortality of thyroidectomy patients in the 19th century (and probably throughout history)? Why didn't the surgeons anticipate this problem? Why wasn't the mortality closer to 100%?