From what I understand, this stems largely from the fact that they were the only major news organization with an embedded presence in Gaza during the Israel-Hamas war (others being unable to get in after it broke out due to the lockdown.) Their ability to report the actions of the IDF and provide graphic images to back it up did far more to generate international condemnation of Israel at the time than any other voice. They played a similar role more recently with a reporter aboard the Mavi Marmara, although he was able to get far less real-time footage out.