Twitter is said to have lost $2.5 Billion/year in advertiser money, largely because Twitter's sales teams have not been returning emails from worried Advertisers. That's a pretty huge impact on Twitter's #1 revenue stream (estimated to be $5 Billion in 2021).
Twitter's core product is advertisements. Without sales staff to keep the advertisers, they're clearly losing a ton of money.
Advertising was always degenerating. I know that over the past year, I've been seeing more and more pornographic material in Twitter, and I'm pretty sure advertisers don't like that kind of stuff. But instead of having teams working out those kinks (pun intended), those teams have been simply fired.
So advertisers know that there's no hope for these issues to be fixed anymore, and are now leaving the platform. There's simply not enough developers left to change Twitter or combat the rise of unsavory material.
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There's been many a blogpost about "Airline advertiser didn't want to have its ads appear next to Airline disasters". (Ex: Southwest's shutdowns cause thousands of flight cancellations, it will be talked about on Twitter... does Southwest want its advertisements being shown next to that??).
These are the kinds of things that Twitter's teams worked to prevent. You know, mundane issues but require _constant_ coding to identify as news events cause a rapid change to the online discussion. And its fair: there's no reason why Southwest's advertisements should be shown in a negative light... or for Southwest to be paying for that kind of negative publicity.