She’s also the only one who called James Comey out as the corrupt liar he is during House committee hearings.
Unlike Haley, Elise will come back from her UN assignment with a bright future as one of the MAGA leaders.
Your second point might be what is going on here. Haley’s primary credential is her stint as UN ambassador. Stefanik will get that credential now, setting her up for a Senate run or a nomination to be VP or even POTUS.