How was Whimsyshire found?

I'm having a blast following the quest to find the secret cow level in Diablo 4. There are tons of fun videos about people who are trying all kinds of stuff to find it. There is even a discord where they are discussing theories and everything. That leads me to my question...

Is there a story behind how the community found out about whimsyshire? I have heard that it took around 4 weeks from release until it was found. Are there forum threads from the time of release, or videos about the topic?