I don't think ISIS organizing on Twitter and other genocides worldwide is something good. But also, Twitter was moderating long before ISIS issues - except it focused on English speaking world (meaning Americans were moderated much more).
More importantly, the events this talk about were in May. That was when advertisers asked questions about future leadership and got no answers. Except what was on Elon Musk tweet feed. And Elon Musk vision as shown on his feed does not add confidence.
There thing are apparently bought a year in advance, so they think a year in advance. Twitter used to spend a lot of effort in order to ensure advertisers year after year. Musk thought it is unnecessary, so he did not. So now they are doubting because communication toward them changed.
Then, as Musk was firing ad accounts managers from Twitter, he had group call with ads who felt not being listened to. Combine it with being unsure who even to talk to, they did not bought again.