Hi blondie, nice question, I can only think of the following points:
Could it be that Adam's fall from perfection made circumcision a health issue for imperfect men? The Bible though does not directly comment on this.
The Bible says that God made it as a sign or as a covenant with Abraham. Buy why Circumcision?
In the Bible, being unircumcised was usually connected with impurity and being obstinate. Stephen told about it during his speech before the Sanhedrin about the covenant of circumcision and called those men as 'uncircumcised in heart'.
During Joshua's time, when the new generation of Israelites were circumcised after crossing the Jordan, God told that he had thus rolled off the Egyptian reproach from them.
Thus circumcision was considered a sign or a covenant of pure worship. However, this was a covenant between a person and God, and was not to be served as a visible sign for other people.
Why did the Hebrews take it seriously as no one could see it and thus get stumbled? Most of the Israelites would have been aware of the case where Zipporah circumcised her son and saved him from God's fury as they neglected the command to circumcise their child. So yes, God directly intervened to punish if the circumcision law was not followed and Jehovah was known for being pretty strict with his rules.
But then, in the first century this practice was discontinued as requirements for being God's people changed.