Perhaps we know, but the reasons will be unpopular.
The only NGO looking for Iran exclusively is Iran Human Right (https://iranhr.net/en/) and depend on the UNHRC, which is not particularly media trained and not good at reacting (also, they lost US funding less than a year ago and are reorganizing as we speak).
In the end, it will be like Yemen or Sudan all over again: media hear of the massacre late, send journalists, journalists get refused, they send journalists to neighboring countries and infiltrate with local guide help, some journalist dies, and three month after the beginning of the trouble we will get images and information.