In preventing suffering, vaccine researchers obviously robbed us of our "free will"... somehow.
That's why God didn't just stop COVID-19: it is necessary because of "free will."
... or at least it was necessary from late 2019 on. Preventing COVID-19 didn't violate anyone's "free will" before that. And at some point in the future - coincidentally, just as scientists and medical professionals eradicate the disease - God will decide that he can once again prevent further outbreaks without violating anyone's "free will."
But right now, stopping COVID-19 would violate our "free will." This is why God isn't doing it.
Makes perfect sense.