Forceful Chief of Staff Grates on Trump, and the Feeling Is Mutual

None of the three - Kelly, Mattis or McMaster are joined at the hip to Trump. They are there out of loyalty to the USA and likely not due to political aims. They've already had impressive careers and achieved a lot. Each has their limit and when it is surpassed they'll do what they think is best at that time. Them leaving would be our loss though, because they each add a level of stability in their own way. They are all thick-skinned and have each been subjected to far worse than Trump could ever dish out. They are human however, and won't take kindly to public rebuke or ridicule, so if that should occur I'd guess they will move on and enjoy their well-deserved retirement.