The fact that lobotomy was often used to treat schizophrenia - a catastrophic failure of rationality - is suggestive.

Unfortunately, it was used to 'treat' so many things that the suggestiveness is lost in the noise.

Really, it was actually used (regardless of the excuses people made at the time) because it rendered difficult patients so tractable and easy to handle in an institutional setting. Pretty much the same reason all the old antipsychotics were used, too.