I am not a Monsanto fan, but I have to give this the benefit of the doubt.
The item of discovery is a "micro-fungal".
I might hypothesis that by killing of large quantities of plants, that we might also be kill what is predatory to fungus.
Just because Round-up isn't also fungicide, should not incriminate it as the cause.
(IE - I shouldn't be accused of increasing your neighborhood mice problem if I take all the stay cats to the pound.)