The first line is the narrative of the MSM that's in bed with government censors and hate that it's no longer controlled by political interests. It is also directly contradicted by independent studies commissioned by Twitter. But speaking of "misinformation", people tend to parrot what they hear whether it's true or not. Thankfully on Twitter that is less effective, thanks to community notes.

Advertisers leaving is a combination of instability caused by Musk's impulsive decision-making, uninformed bandwagoning based on the perception projected by aforementioned MSM and parrots (AKA peer pressure), and the state of the economy combined with the above forcing them to reevaluate their investments. Advertisement revenue has been dropping everywhere as it turns out.