It's not about being man made or genetically engineered. Scientist believe the virus was being studied in bats in a lab in Wuhan.
PolitiFact - What we know about the source of the coronavirus pandemic
I'm not sure why this is such a mystery, the Epstein-Barr (mononucleosis) virus presents the same. If you had mono as a child you can go get the test today and it will be positive for Epstein-Barr virus. Same with Varicella zoster virus which causes Chicken Pox and later in life presents as Shingles.
