Trump is angry
Trump's victory speech tonight struck me by how angry it was, especially after his attempt to be a little more conciliatory following Iowa. He wouldn't even mention Haley by name, calling her an imposter instead. He suggested her ally Sununu was on drugs, and brought on Ramaswamy to launch more invectives in her direction. If you're Haley, and you relish getting under Trump's skin in a way that few other candidates have managed so far, why are you going to drop out? Haley is wily and has delighted in running against those who have dismissed her for as long as she's been in politics, so I imagine speeches like Trump's tonight only fuel her.
—Jacob Rubashkin, Inside Elections