For example, the average lifespan in the US of someone 80 years old is 8 years. If the likelihood of death is the same every year(not realistic but good for a first estimate), then the expected death rate is over 8% per year just from age. Make that even even worse by selecting nursing home patients instead of the general population and you can easily get over 20% over almost three years.
The 20% rate on certain batches demands investigation, not panic or witch-burning.
Your post is precisely on point and very thoughtful. Thanks.