When people start flooding off the service and the only people left are nazis and bots, what will their revenue look like then? It'll become the reddit of social media, with small, reasonable groups overshadowed by overwhelmingly toxic, hostile, and destructive forces.
How long until their blind eye towards harassment, racism, abuse, and booting collapses any value they have? How long until the average person perceives Twitter as a place where racists congregate and no one else can bring themselves to visit?
And when it does, will they pull a reddit and suddenly grow a conscience, miraculously saying "Oh there's a problem on our service and we're going to charge to the rescue!", or are they going to go 4chan and hide behind "freedom of speech" to excuse the filth their platform breeds?