Reverse network effects from an exodus is how social networks die, when all your friends and influencers leave to Threads/Bluesky you'll leave. Elon get less revenue from less users, cuts even more, worsening the product, fueling the exodus. Vicious cycle all the way down. After trying his hand a influencing politics, he'll get tired of the money pit and offload it at a loss or straight up shut it down.
If twitter gets him political wins then that'd be a success, but there are other billionaires out there getting their way politically without burning $50bn or the public scrutiny.
Sure it's worse for advertisers but is that really what we base success on?