How long does it take to research and develop a new vaccine? was probably viewed so much because it was cited by The New York Times article in 2018 to back up a claim that “it takes 10 years and more than $1 billion to develop a vaccine” (which obviously wasn’t talking about the kind of situation were are in now). And I imagine that the New York Times article got some reads in 2020 as it became very relevant.
It performed well in some google searches, probably partially because of that link. I would guess that most users game from google, but I haven’t checked, I just remember it doing well when I looked in ~May.