I feel bad for Hemmingway. He killed himself because he was depressed (which he didn't realize that on it's own, he could handle), and didn't realize his personal Hell could always burn hotter, and Electroshock Therapy was advertised as the new, true treatment for depression. Obviously he unfortunately didn't put enough thought into (or didn't have the access to research) the potential affects of such therapy, what epileptics go through, the potential affects of seizures (even just one), and what extreme or radical psychological therapies of his near-distant past (such as lobotomies..) resulted in, and what they originally promised to do.. He put way too much trust in doctors; to this day, electroshock therapy is banned in some European countries because the data on it doing more harm than good is sketchy at best, and everyone's brain is unique.

After receiving his first induced-seizure, he was never the same, and this is what lead to him killing himself. Seizures and epilepsy are very stigmatized and misunderstood:

"Ernest Hemingway, an American author, died by suicide shortly after ECT at the Mayo Clinic in 1961.[127] He is reported to have said to his biographer, "Well, what is the sense of ruining my head and erasing my memory, which is my capital, and putting me out of business? It was a brilliant cure but we lost the patient."

The feeling of his "capital", or his mental faculties being taken from him, is a symptom (short or long-term) of the postictal state after a seizure. Regardless of who he was or what he did, no living being deserves to experience that state of being, and so strongly that it pushes them to suicide.