Why he didn't have Pompeo and Bolton be in the loop, I don't know, but it's certainly in character.
This is the defining feature of Trump's leadership style, such as it is, and one he learned in bastardized fashion from Fred Trump. He never writes anything down and telegraphs as little as possible so that everything can be changed to suit the needs of the moment, which only exacerbates what look like symptoms of dementia since no one can tell if he actually remembers saying whatever's contradicting what he's saying now. Pompeo and Bolton didn't need to know in order for Haley to resign, and there is only ever one thing going on at a time in Trumpworld so it's inconceivable that her resignation might have any sort of broader impact necessitating that they be informed.
Without speculating on her motivations, I think we can say that now is a good time for less-loathed Trump officials to get out. The odds of Trump doing something titanically stupid increase as the midterms approach, and after that the MAGA agenda is likely to hit significant roadblocks. Even if Trump weren't the glory hog he is, there's not going to be much left to take credit for and a lot of blame to go around going forward.