I remember discussing the blood doctrine with some uninformed JWs. They were under the impression that the blood doctrine had been established as soon as transfusion was invented. I said: not so, the blood doctrine was established in 1945 , blood transfusions had been pioneered in the late 19th century and the blood types had been discovered in the early 20th century. So neither Russell nor Rutherford championed it; it was historically recent.
The question is, if it is patently unbiblical to have a blood transfusion, why did it take them so long to figure it out?