Early "medical" proponents of male circumcision promoted it as a "cure" for anything from masturbation to a long list of other maladies. It was pure snake oil. But it was only after 1945 that the practice started gaining any widespread adoption in the United States. Elsewhere around the non-Muslim world it was (and remains) basically unknown and restricted to religious practice. Interestingly, the main exception is Korea, for unique reasons.
After 1945, millions of men returned from war where the U.S. military "clipped" most of them for "hygienic" reasons as it was touted as a way to help prevent G.I.s from contracting various venereal diseases. As these men became fathers, they passed on the practice to their sons. And, thanks to the rise of hospital births and the fact that this was now "covered" by insurance, this became basically a profit center for the medical establishment. As good businessmen, doctors began promoting all sorts of "benefits" to the general public. But it's the same snake oil just dressed up in more respectable garb.
The case of Korea is interesting because after 1945 with the American occupation, Americans were viewed as "modern" and "advanced", so Koreans wanted to "be American" and so adopted male circumcision essentially as a sign of admiration. The difference is that in Korea it's typically performed on boys around their 12th birthday, where family and social peer pressure ensures that "consent" is obtained.
Interestingly, Western medicine never took the same attitude towards female circumcision, which is why the U.S. can still regard it with horror while considering its male counterpart as "normal". Stripped of the specious medical claims, both are anything but normal. This is the only area of "medicine" where the attitude is that humans are "defective by design" and require universal surgical "correction" to address this defect.
Interesting. Have you evidence that the medical claims are specious?