The thing I just don't understand is why gain research would take the effort of making the virus much less deadly. This virus is around ten times less deadly that SARS, wouldn't gain research at least maintain virulence?
Another way of discovering what increases property X is testing that some change indeed increases property X, while also discovering it decreases property Y.
While attempting to increase both X and Y, they made an intermediate with increased X and decreased Y. Perhaps it seemed a promising starting point to also increase Y.
I don't get the surprise. This is all par for the course in research.